'I COULD not deny that I loved participating in Washington's great contest." With these words Clark Clifford sums up a career of more than 45 years as a Washington lawyer, White House aide, Cabinet officer, and adviser to presidents. Over these years other men have had a greater influence on national affairs than or very near the pinnacle of the United States power structure. This is his story, written in collaboration with Richard Holbrooke, a former assistant secretary of state in the Carter administration. Like many another young man, Clark Clifford landed at a desk in the White House by an accident of friendship, under the wing of a Truman appointee in 1945. In the first manifestation of what would prove to be his special talent, however, Clifford quickly earned Harry Truman's complete trust. Designated counsel to the president soon after his arrival, Clifford - just 38, a successful St. Louis trial lawyer but, as he acknowledges, without a shred of experience in politics or public affairs - was closely i nvolved in every major act of the Truman administration until he left midway through the second term. Clifford describes how, working a tier below the great creators of America's postwar foreign policy like George Marshall and Dean Acheson, he participated in developing the Truman Doctrine and the Marshall Plan; helped devise the major restructuring of the national-security apparatus that produced the Defense Department, Central Intelligence Agency, and National Security Council; soldiered with Truman in facing down labor bosses and breaking new ground on civil rights; and rode the train and wrote speech es during Truman's whistle-stop upset of Thomas Dewey in 1948 (all the while superintending the president's regular poker evenings). In 1950, Clifford launched what was to become his singular law practice. In his words: "I became a practitioner in the arcane art of advising some of the nation's leaders and would-be leaders." These included, with obvious significance for his career, John Kennedy and Lyndon Johnson. (Another early client was the eccentric and secretive Howard Hughes, whom Clifford, despite years as Hughes's man in Washington, never met.) Kennedy's restoration of the Democratic dynasty in 1960 brought Clifford back prominently into public life. Although Clifford had backed his fellow Missourian Stuart Symington for the nomination, JFK soon took him on as a favorite go-between in sensitive personal and political matters. Clifford acknowledges that he was never as close to the detached Kennedy, however, as he was to become to President Johnson. The lawyer became one of Johnson's closest advisers, first as a private citizen and then, in 1968 , as secretary of defense, succeeding the exhausted and disillusioned Robert McNamara. Nineteen sixty-eight, the year of Tet, of the Eugene McCarthy insurgency that drove Johnson from office, of the tumultuous Democratic convention in Chicago, was the pivotal year of the Vietnam crisis. In that year, the US ended its mired pursuit of military victory and, with the Oct. 31 bombing halt, commenced its drawn-out but irrevocable disengagement and quest for a negotiated settlement. Clark Clifford was the leading advocate of the new policy in the administration. However one feels about US policy in Vietnam, it must be conceded that, in his brave and tenacious fight to end a war he believed was damaging America, this was Clifford's finest hour. He recounts his often lonely struggle in fascinating detail. Throughout his distinguished public career, Clifford has been that rarest of Washington creatures: the nonsycophant who can give the powerful - including presidents - his unvarnished advice without losing their confidence. He also is a decent man. He must have made his share of enemies (though perhaps fewer than less polished wielders of power), but for a Washington memoir his book is refreshingly devoid of score settling. The large cast of characters that people his book - including many with whom Clifford clashed on policy issues - are recalled usually with respect, often with fondness, unfailingly with fairness (and many times in entertaining anecdotes). Drawing on his experience, Clifford also offers sage counsel on such matters as the proper role and demeanor of White House aides (John Sununu, take note), the value to presidents of disinterested outside advisers, and the impropriety - based on his observation of Abe Fortas - of Supreme Court justices acting as presidential counsellors. There is another side of the Clifford saga, however, one that is nearly invisible in this 700-page book. Of his 46 years in the nation's capital, he has served only six in government, although over the years he has performed many other discrete governmental or quasi-governmental tasks. The rest of the time he has been the man Joseph C. Goulden in his book "The Superlawyers" called Superclark, the Washington Lawyer par exellence - the opener of doors, the behind-the-scenes operator for powerful corporate interests. It's crass and misleading to characterize plugged-in Washington lawyers like Clifford or Robert Strauss or Lloyd Cutler as "fixers" or "influence peddlers." Nonetheless, the work that lawyers like this do - largely out of the public eye and unchecked by political accountability - in shaping America's laws, regulations, and administration of justice to the interests of their wealthy clients is little understood and thus overlooked. Clifford could have performed a signal public service by explaining exactl y what it is he does for his six-figure fees. It's as Superclark, not as Clark the Wise Man, that Clifford is suffering through an ignominious coda to his illustrious career. He is at the center of press and law-enforcement investigations into the secret ownership of a bank Clifford runs - ownership by Arab investors implicated in laundering drug money. Whether Clifford knowingly misled bank regulators or, as he insists, was duped himself, the luster of his legend has been tarnished. All the more reason why this ultimate insider might have used his memoir - so illuminating on his public life - to throw light on Washington's murky, revolving-door, off-book legal world in which he has moved for many years.