Accessory is a hit (4)
I believe the answer is:
belt
This clue is a double definition.
'accessory' is the first definition.
(belt is a kind of accessory)
'a hit' is the second definition.
(I know this)
'is' acts as a link.
(Other definitions for belt that I've seen before include "See 24" , "sock or > tie" , "Big hit" , "A vigorous blow" , "Race" .)