Cruelty (6)
I believe the answer is:
sadism
'cruelty' is the definition.
(deriving pleasure from cruelty)
This is all the clue.
(Other definitions for sadism that I've seen before include "Deliberate cruelty" , "Perverse pleasure" , "Enjoyment taken in inflicting pain or cruelty" , "Dim ass (anag)" , "Love of inflicting pain" .)