THOUGH NEARLY ALL eyes on Capitol Hill are momentarily riveted on the center ring where the Great Ax-Throw Act is in progress, another act is getting under way that may feature even more rough-and-tumble political gymnastics: It's the Clean Air Act, which is due for congressional reauthorization by the end of September. For a while, it looked as if cool heads prevail to avoid bitter wrangling; but unless a bipartisan coalition of legislators does some quick footwork, there may be little hope for timely, reasonable action.

With hearings starting up in both the House and Senate, already there are scores of bills calling for all sorts of changes in the Clean Air Act -- some sound, some not. These, plus the sheer scope of the act itself, add up to a complicated period of consideration and debate even without sharp confrontations; but environmental groups seeking stronger provisions and industries that want the act softened are so far nowhere near meeting each other halfway.

Among the more difficult issues, for example, is the balancing of air pollution safeguards with efforts to develop new energy supplies -- how much and how elaborate against how little and how efficient. All sides are concerned, too, that the many extremely technical questions may make impossible any sophisticated consideration of the act.

Sen. Robert T. Stafford (R-Vt.), chairman of the Senate Environment and Public Works Committee, and Sen. James A. McClure (R-Idaho), chairman of the Senate Energy Committee, are in the forefront of those warning about the dangers of confrontation and "major overhaul" -- as well the harm that delay could cause. For example, extended delays could hurt industry's efforts to anticipate and/or calculate the impact -- make that read, cost -- of future clean air standards that might have to be met.

Still to come -- and nowhere in sight yet -- are President Reagan's own proposals for changing the law. So far, all that has emerged is the nomination of Anne M. Gorsuch to head the Environmental Protection Agency, which has caused justifiable anxiety among Republicans as well as Democrats on the Hill; they note that her thin credentials for such a complex job come at a time when strong, knowledgeable and respected leadership should be the order. Regardless of the outcome of this confirmation process, agreement on clear air legislation had best not carry over into 1982 -- unless all sides are willing to let election-year politics replace sober deliberation of the health, energy and economic implications of an important piece of legislation.