AS THAT HUGE congressional conference on the trade bill gets under way, most of the members are familiar with its more prominent provisions. But does anyone really know what else has been tucked away in it? There's quite a list of little items dropped here and there in those thousand pages, often with no benefit of hearings, most of them sharply protectionist and capable of doing great mischief to American trade while serving the special interests that promoted them.

Here's one example: Sen. Ernest F. Hollings, who ought to know better, persuaded the Senate one day last June to accept a brief technical amendment regarding dumping. It is pure poison ivy.

Dumping is the unfair practice of selling goods abroad at less than the price in the producer's country. The concept is simple enough. The tricky part of a dumping case is the complex process of stripping away incidental costs -- transportation, for example -- to calculate truly comparable prices for the goods in both the home market and the export market. One very substantial item is what the lawyers call indirect selling costs -- advertising, promotion and so forth. American courts have held, reasonably, that it is fair to deduct indirect selling costs from both the home and the export prices.

The Hollings amendment, in contrast, would require deduction of the indirect selling costs from the export price, but not the home price. That would deliberately distort the comparison and make it easier -- much, much easier -- for companies to win dumping cases here in the United States and get protection from their foreign competitors.

It's an exceptionally bad time for the United States to set protectionist precedents. Over the next several years, if the United States is to reduce its dangerously large trade deficit, American imports are going to have to come down and American exports are going to have to go up. Foreign trade will begin to have the same impact on foreign countries' markets that it has been having here. If the United States now enacts a fake and tilted definition of dumping, other governments with domestic producers to placate will gratefully seize it with both hands and start hitting American exporters with it.

Sen. Hollings' little technical amendment isn't the most important part of the trade bill. But it could do real damage. If it's enacted, it will do far more to restrict exports out of this country than imports coming in