Sadistic (5)
I believe the answer is:
cruel
'sadistic' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cruel that I've seen before include "Deliberately and pitilessly causing pain" , "Merciless" , "Lucre (anag.)" , "Inflicting pain without pity" , "Savage; harsh" .)