This season:; Flexibility with a touch of fantasy

The encouraging word for the timorous shopper this season is that most of her concerns may be put aside. For in the kindness of their hearts (or in the interests of their profit margins), American's clothesmakers have largely foreseen her fashion forebodings.

She is not, by any means, being called upon to trash all the clothes she owns an rush out to buy ba fresh lot of fashions to meet the specifications of an entirely new set of style rules. Nor is she bound to the single shape, the one-and-only hemline, the this-is-it look, the color of the week (although the purple, violet, cyclamen, and fuchsia rage carries on). Nor is she being told that what she feels most comfortable wearing will necessarily mark her as an outmoded frump.

On the contrary, fashionmakers understand her plight in this period of fickle economics. They seem to have considered every eventuality and then made a point of covering all the bases.

She is therefore at liberty to choose almost any style that pleases her. If shoulders with padding turn her off, there are other acceptable ways of adding emphasis to the top of the silhouette. A capelet, a tiered ruff collar, epaulets, a full sleeve with top-pleating or gathers, or a rounded cut will do the trick.

her waistline (like her hemline) is not immutably fixed at one place. It may in fact be nonexistent if she is wearing a loose chemise style. Other modish belt lines range from the natural waist to low down on the hips, the dropped torso or tunic look being dear to the hearts of many designers at the moment.

As to skirt lengths, absolutely none can be rules out entirely. The suggestion for those who for one reason or another require a conventional hemline is "just below the knee," but no one is insisting on this.

Although "Are skirts shorter?" is a reasonable question, this season's answer ("Yes, but not always. . . .") is waffling. "Length is unimportant," Yves Saint Laurent has said, implying that the subject has become tiresome. How free the length choice may be was illustrated at pret-a-porterm fall openings in Paris where several designers sent groups of models out on the runways in everything from micro-mini to ankle skirts.

Flexibility also applies in the matter of shapes. Pinched-in waists and tight straight skirts have been sent into oblivion. But aside from the emphasized shoulder and full sleeve, a narrow silhouette has as much fashion validity now as a voluminous look.

Speaking of volume, some of the all-encompassing outer coverings shown over short skirts and knickers recall the Big Look of not too long ago. Recycling clothes left over from recent years is in fact a distinct possibility this fall, as a good many of them are having an early comeback. Among the reruns returned to fashion currency are ponchos, capes, kilts, shawls, Pierrot collars, peasant smocks, and clinking-coin gypsy jewelry.

What goes under the outer covering is less likely to be a suit this year, which is not to say that suits are suddenly demode.m Spencer jackets and pleated skirts, contrasting tweed jackets with solid wool skirts, tailored blazers with matching flannel trousers, and above all, the velvet combinations of skirt with velvet-trimmed jacket, play more than minor parts in the autumn picture.

The stars are the sweaters -- in Shetland, lamb's wool, cotton, angora, and often mohair, the natural fiber that is less expensive than costly cashmere but just as light, soft, and WArm. Knits and classic separates remain the backbone of most wardrobes, but with a difference: They are assembled in innovative ways.

A costume exhibition and a French coutourier account for certain fantasy influences. Hapsburg looks have entered in by way of last winter's show of Austro-Hungarian Empire regalia at New York's Metropolitan Museum of Art. Folkloric Peruvian motifs may be traced to the printed blouses, skirts, and shawls that fashion power Saint Laurent used for his fall Rive Gauche collection. Also strong are the Scottish and Victorian touches with which fashion has been having a continuing flirtation.

Worth watching to see where it will lead is the reintroduction of pants, of all types this time. These include knickers and gathered culottes which resemble skirts, both shown for various hours of the day.

Still with us are stunning graphics, color splits, and -- for evening in particular -- asymmetrics, with the one-shouldered dress and the dipping hemline much in evidence.

Nothing borders on the freaky. What has left us in this year of lean pocketbooks is the perilously far-out.