Flea-market fashions at designer prices; Paris collections reflect a trend based on shock rather than chic

Generally, being well dressed means to appear neat and tidy at all times, with scrupulous attention to small details. When heels start to wear down, off they go to the shoemaker for repairs. Missing buttons are promptly sewn back on, and inadvertent tears mended or rewoven. Stockings with runs are instantly discarded, and the well-groomed woman does not step out the front door with her hair looking like a cross between Woody Woodpecker and a King's Road punk.

But an astounding fashion trend has emerged in the past two years, based totally on shock rather than chic. Many basically pretty young girls are turning out as counterparts of the Paris clochardsm (hobos and park-bench bums) in a careful assemblage of tatters often picked up at the flea market. This inexplicable appeal of poverty is rumpled, crumpled, ragged, and bedraggled, with enough built-in holes to put any moth out of business. It is ''survival dressing'' best suited to beggars, but sad on the streets of Paris.

Yves Saint Laurent's genius has always been his uncanny knack for adapting trends that are already out in the streets. But the king is having no part of this flea-market affair or anything vaguely slovenly or unkempt. Instead, we have several of the Japanese contingent showing in Paris to thank for ''tortured chic,'' often featured at prices that are equal torture for the pocketbook.

Rei Kawakubo of Comme des Garcons made the original breakthrough with her first collection shown here two years ago. It was extremely controversial, yet many professional buyers raved over the layered garments full of Swiss-cheese holes, raw edges, and jagged hemlines, complete with cadaverous makeup and the occasional twist of a prize fighter's black eye blooming on one side of the face.

Although Comme des Garcons (Like the Boys) might more aptly be titled Comme des Clochards (Like the Tramps), these garments, plus others in many French collections, are not exactly given away. They may be made out of what appears to be potato sacking, cheesecloth, or old dust rags, but the actual fabrics are often handloomed and suitably expensive.

French designers, after a long and appraising gaze at freaky fashions from the Land of the Rising Sun, have taken a high jump on the bandwagon. Daniel Hechter, creating primarily for the under-30 crowd, sent his mannequins down the runway to present fall and winter collections, garbed in voluminous, shapeless things that he says were inspired by ethnic garments from the steppes of South America. One size appears to fit everyone from the midget to the circus fat lady. The total cost of most ensembles amounts to over 4,000 francs (about $500) , not including the lumberjack shoes or paratrooper's boots. You're also on your own for the frazzled homemade hairdo to complete the effect. It needs no tender loving care from a top coiffeur.

If rich girls want to look poor, that's their business. But anyone opting for authenticity is best off out at the flea market, where it has all been going on for centuries. There, one can pick up genuine shabbiness at bargain prices. It is a look the average wardrobe would benefit most from doing without.