Circus under a real tent -- in New York!

What's as much fun as a three-ring circus? A one-ring circus, of course - if it's the Big Apple Circus, which makes up in charm and intimacy what it lacks in hugeness and hoopla.

Billed as New York's only resident one-ring circus, the Big Apple recently set up shop at Lincoln Center in a whopping 1,600-seat tent tucked neatly between the Metropolitan Opera House and the New York State Theater. It's a modest show compared with the extravaganzas given each year by the Ringling Bros. and Barnum & Bailey bunch, who have decades of experience and all of Madison Square Garden at their disposal.

But smallness can be a virtue, even at the circus. It's a pleasure to see first-rate acts close up, one at a time, enjoying a real rapport with their audience. And it's great fun to see a circus in a genuine tent for a change, complete with sawdust and sandbags.

The spectacle begins with a traditional ''charivari,'' with the performers parading before the crowd, and you can tell right away this isn't the biggest show on earth. There are just over a dozen acts on the program, plus intervals with a couple of clowns named Michael and Paul - one of whom, Paul Binder, is director and founder of the Big Apple Circus, which may explain why he pops up more often than anybody else. It's a typical lineup, with trapeze artists, jugglers, a couple of trained animals, and other pleasantly predictable stuff. But it's all on a human scale, less overblown and overhyped than the three-ring variety. Even the ringmaster reaches his audience on a reasonably calm and dignified level, without the bellowed ballyhoo that seems to be de rigeur in larger and splashier shows. The music is provided by a small but energetic crew - including drummer David van Tieghem, normally a stalwart of the avant-garde fringes - who acquit themselves with proper noisiness, though leaning toward disco a bit too strongly for some tastes.

The stars of the circus lineup are easy to spot, because the places of honor - just before intermission and just before the finale - are reserved for them. The first half of the program winds up with Philippe Petit, the high-wire wizard who became famous a few years ago for staging an unscheduled stroll between the towers of New York's tallest building, the World Trade Center. He isn't a particularly charismatic performer, but he certainly knows his stuff, and working without a net is a suspenseful business even in the comparatively down-to-earth confines of the Big Apple tent. The other main event is a splendid trapeze act by the Flying Goanas, which looks downright spectacular in such intimate surroundings.

Other highlights include the Back Street Flyers, handspring specialists from Harlem; a quietly competent juggler who climaxes his act with a fire dance in the darkened tent; a literate and very funny juggling duet by the clowns Michael and Paul; a couple of acrobats; and a gang of trick unicyclists who are likable if not very versatile. Among other attractions are a gent who balances upside-down on his hands and a trick horseback rider. Not to mention Tarra, who was billed to the press as ''the world's only roller-skating elephant,'' but confined himself (herself?) on opening night to such accomplishments as swigging a soft drink and playing a harmonica, very softly.

Children of all ages seemed to enjoy the show during its first performance of the season, and it should have little trouble drawing crowds through Jan. 3, when it will fold up its tent and move on.