Piece of refereeing equipment (7)

I believe the answer is:

whistle

(Other definitions for whistle that I've seen before include "L.S.White (anag.)" , "What ref blows" , "Pucker up and blow" , "For something, ask in vain" , "Call vainly for" .)

I've seen this clue in The 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.