EVERY sharp secretary needs a pencil. Only, in this age of the modem, we're talking about skirts not writing instruments. For that office staple - the slender, knee-length tailored skirt - is setting fashion hemlines in the workplace once more this season.

It's all part of fashion's renewed fixation with the real-life clothing needs of the working woman . . . a woman, that is, who needs clothes which fit a professional lifestyle which can't accommodate the flightier departures into fashion fantasyland . . . a woman spending her own hard-earned cash. Her 9-to-5 sartorial demands dare not be ignored.

Function and value may be her principal concerns. Practicality is important, too. But that doesn't exclude scope for a little frisson of excitement - what you might regard as reduced-calorie fashion fizz.

Careerwear's new fashion-lite diet combines the pencil skirt with sleeveless shell tops, twinsets, or a combination of sweater and shell. The look is not as menacingly buttoned-up as the eighties power suit. But in those svelte skirts and those killer heels, you sense the lady means business.