Cruelty is admitted by sorrowful male (6)
I believe the answer is:
sadism
'cruelty' is the definition.
(deriving pleasure from cruelty)
'is admitted by sorrowful male' is the wordplay.
'admitted by' is an insertion indicator.
'sorrowful' becomes 'sad' (associated in meaning).
'male' becomes 'm' (common abbreviation).
'sad'+'m'='sadm'
'is' inserted into 'sadm' is 'SADISM'.
(Other definitions for sadism that I've seen before include "The love of cruelty" , "Deliberate cruelty" , "Dim ass (anag)" , "Cruel behaviour" , "Taking pleasure in cruelty" .)