Cheek eaten by an evil murderer (8)
I believe the answer is:
assassin
'murderer' is the definition.
(I've seen this before)
'cheek eaten by an evil' is the wordplay.
'cheek' becomes 'sass' (both can mean rudeness or insolence).
'eaten by' is an insertion indicator.
'an' becomes 'a'.
'evil' becomes 'sin' (I've seen this before).
'a'+'sin'='asin'
'sass' inserted within 'asin' is 'ASSASSIN'.
(Other definitions for assassin that I've seen before include "Terrorist" , "butcher" , "hit man" , "Asians SS? (Anag)" , "I kill" .)