Criminal crows about coming back (8)
I believe the answer is:
murderer
'criminal' is the definition.
(I know that murderer is a type of criminal)
'crows about coming back' is the wordplay.
'crows' becomes 'murder' (I've seen this before).
'about' becomes 're' (regarding).
'coming back' shows that the letters should be reversed in order.
're' backwards is 'er'.
'murder'+'er'='MURDERER'
(Other definitions for murderer that I've seen before include "Assassin" , "Criminal killer" , "Serious criminal enters demurrer" , "One commits homicide" , "hit man" .)