All the world loves a clown, they say, and buyers and some designers are banking on American customers liking the Pierrot look for fall. Like Pierrot's, the style has a ruffled, stand-up collar and a very full tunic or dress.

The look has shown up in several shows that started the week-long marathon of fashion presentations for international buyers and the press in Paris this week. The silhouette came through loud and clear in the France Andrevie show where layers of lace created a ruff at the neckline of very full dresses in crepe de chine. There is a similar look at Cacherel and the Pierrot theme is expected to come up again at Dior next week.

Not since Elizabeth Taylor's ruffled neckline blouse, created to hide the scar from her tracheotomy in London in 1961, has there been so much talk of ruffled necklines. At that time the ruffled neckline blouse with the ruffle repeated down the front suddenly influenced dresses, sweaters, nightgowns and eventually housedresses.

The reasons for this new style are less easy to pinpoint. "It seems to clearly mark the end of tough chic," says Jean Rosenberg of Henri Bendel. "Everything now is soft and loose, even the hair is longer and freer and softer. And this silhouette is a pretty example of this new direction."

Sally Frame of Saks Fifth Avenue ties the look to the ruffled blouses Saint Laurent showed under suits in his couture show in January. She and the store's blouse buyers have already ordered blouse versions of the look. (Actually such a neckline showed up as a Gloria Vanderbilt trademark in her first collection but it sook Saint Laurent's sanction to make it happen.)

Marc Bohan of Dior says he'll carry out this look with big, full, unlined coats as well as a few dresses when he when he shows his fall ready-to-wear on Monday. "Everything is looser because it is more comfortable," says Bohan, who sometimes wraps the midriff or puts in an elastic or drawstring to mark the waistline, or just lowers the waistline in his styles. Like other designers, the pants he will show will be skinny but they will be worn with very big, baggy sweaters or very full tunics. "Fat people don't want to admit it, but they look better in loose things than the tight styles they prefer to wear. Tight things make you look bigger because they accentuate the bulges," he adds.

At Popy Moreini, a boutique in the Les Halles section, you can already buy a Pierrot collar as a dickey, a separate item to attach to the clothes you already own. Mimi Liebeskind of Anh Taylor thinks that's a good way to achieve the look. "Imagine a Pierrot collar being worn with a baggy sweater and printed skirt. It makes as much sense as the collar worn with a loose dress. As a separate collar you can wear it both ways," she says.

Buyers, who are serious about the clown look, are finding the price tags on them no laughing matter. To make the style successful, designers have chosen the lightest weight fabrics, which also are the most expensive.

"Yes, the prices are up from this time a year ago, because all the clothes are fuller," says Chantal Tousseau, fashion director of the AMC office here which acts as a guide to many stores including Woodward & Lothrop. "But it makes no difference. The look is so fresh and new, it will be snapped up regardless of the cost."

For proof of that, the fashion world will have to wait and see.