That little thing you do?

TIC

Think of an involuntary twitch or habit—like a nervous blink or a repeated motion—that’s often small and hard to control.

The clue plays on the phrase "that little thing you do," which is a common way to describe a nervous or habitual twitch—often called a "tic." It’s also a nod to the song "That Thing You Do" by The Wonders, where the word "tic" sounds like a short, repeated action. The answer is simple and literal, fitting both the definition and the playful hint in the clue.