Rounds out, as an event (4)

I believe the answer is:

caps

(Other definitions for caps that I've seen before include "Head-coverings" , "Coverings for heads or bottles" , "Crowns" , "Coverings, for heads say" , "Bottle tops" .)

I've seen this clue in The New York Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.