Hit Western with bad actor (4)
I believe the answer is:
wham
'hit' is the definition.
(whamming is a kind of hitting)
'western with bad actor' is the wordplay.
'western' becomes 'w'.
'with' is a charade indicator (letters next to each other).
'bad actor' becomes 'ham' (I've seen this before).
'w'+'ham'='WHAM'
(Other definitions for wham that I've seen before include "Strike -- 1980s' pop group" , "Sound of heavy blow" , "Come down hard on" , "Eighties pop group" , "striker may do so" .)