Sit tight

BIDE

Wait patiently, as you might when expecting an opportunity to arise.

"Sit tight" is a common phrase meaning to wait patiently, which directly hints at the answer "BIDE"—an old-fashioned verb for staying in place or waiting. The clue plays on the literal and figurative sense of holding your position, with "bide" fitting neatly as a concise synonym. It’s a straightforward definition without hidden wordplay, relying on the solver recognizing the less common word for a familiar idea.