Expresses appreciation for a performance, say

CLAPS

Think of the sound an audience makes when they enjoy a show—it’s often done with the hands and can be loud or quiet.

This clue hints at a common way to show approval after a show or concert. "Expresses appreciation for a performance" points to the action of applauding, which is what "claps" means. The word "say" signals that "performance" is just one example—you might also clap for a speech or a good joke. The answer is straightforward: the verb "claps" fits both the literal action and the clue’s phrasing.