THE coup in the Soviet Union is a desperate attempt to turn back the clock. Its engineers are reactionary elements in the Communist Party with active collusion of the internal security apparatus. The Ministry of Interior has its own armed forces; together with the KGB, its communication network covers the country. The military-industrial establishment is in the conspiracy, and Defense Minister Dmitri Yazov's at least nominal participation betokens Red Army support. It is an impressive combination which nonetheless may very well fail. The Soviet republics and the world community must now clarify their minds about glasnost and perestroika, the successes and failures of the Gorbachev years. Despite some window-dressing assurances about respecting treaties and a promise to continue domestic reform, the authors of the Monday morning coup in Moscow can hardly survive such scrutiny. The world now sees what it has at stake. While the clock cannot be turned back in Eastern Europe, the Gorbachev momentum that stimulated and sustained the incredible changes of the past three years has, for the moment, been broken. President Mikhail Gorbachev is not likely to survive in office even if the coup fails. What will happen to the more open political climate that he helped to create? So much of what has been done since the end of the Iran-Iraq war and the Soviet withdrawal from Afghanistan has stemmed from the Kremlin's new mode of cooperation. Epitomized in unity of action by the five permanent members of the United Nations Security Council, it has fulfilled the original promise of the UN as peacemaker and peace-keeper. Security Council resolutions, which old Soviet policy would have vetoed, have broken new ground. Most dramatically, in repulsing Iraq's aggression last year and since then in the complexities of postwar policy, the United Nations has been able to act. A new dimension, with worldwide implications, was outlined in the finding that Iraq's oppression of its Kurdish population justified intervention as a human-rights violations that threatened international peace. Gorbachev's foreign policy has brought the solution of bloody confrontational problems in southern Africa. It has taken the Cuban thorn out of America's flesh and offered the prospect of cooperation for peace in Central America and Southeast Asia. Outstanding also is the dilemma of Israel, its Arab neighbors, and the Palestinians. A Middle East conference depends on Soviet-American joint chairmanship. Both Israel and the Arabs have a major concern in the continued immigration of Soviet Jews. WITH Moscow no longer interested in radicalization, a resolution of the Cyprus tangle moved within reach. The Secretary-General of the United Nations is able to fulfill his natural role as nonpartisan intermediary in highly charged matters like the release of hostages and the care of refugees. The West must now seriously consider what it can do to ensure that the interruption of this process by the Soviet coup does not lead to its reversal, while at the same time not openly intervening on behalf of Gorbachev. For their part, the people of the Soviet Union must consult their interests. These certainly do not lie in the toleration of the forces which gave them 70 years of terror and stagnation. Gorbachev has bitterly disappointed the Soviet public's hopes for a better life, but they have learned in the past six years that they are no longer passive victims of a ruthless regime. There must be, still, a residue of fear that will keep many people on the fence. But, on the whole, the mystique of the state, not to mention the Communist Party, has been broken. People have come to realize that they have power. The dominant republics in the Soviet Union have turned away from recentralization of authority. The Army has serious cracks, ethnically as well as generationally between younger professional officers and old fat cats of the status quo. Perhaps Boris Yeltsin, popular president of the Russian Republic, will be the catalyst for a new and decisive move to crack and discard the outmoded Soviet mold.