Bit of a blind

SLAT

A thin, horizontal strip that helps control light when windows are covered.

"Bit of a blind" is a clever way to hint at a part of window blinds. The word "blind" refers to the window covering, and a "bit" of it would be one of the horizontal strips—called slats—that make up the blind. The clue plays on the double meaning of "blind" (both the covering and the idea of not seeing) but focuses on the physical object. So, the answer is "SLAT," the individual piece you adjust to control light.