Whack gets boxing prize (4)
I believe the answer is:
This clue is a double definition.
'whack' is the first definition.
(I know that whack can be written as belt)
'boxing prize' is the second definition.
(I've seen this in another clue)
'gets' is the link.
(Other definitions for belt that I've seen before include "Hit hard; leather strip" , "It's worn around the waist" , "Trouser support" , "Sign of rank in karate" , "Flog -- band" .)