A smack on the wrist (4)
I believe the answer is:
cuff
I believe this clue is a double definition.
'a smack' is the first definition.
(both can mean to hit)
'on the wrist' is the second definition.
(I've seen this before)
(Other definitions for cuff that I've seen before include "There may be a link with this" , "Hit with the flat of the hand" , "Sleeve ending" , "Strike" , "Blow - on the wrist?" .)