Old lady's practically divine butcher (8)
I believe the answer is:
massacre
'butcher' is the definition.
(I've seen this before)
'old lady's practically divine' is the wordplay.
'old lady's' becomes 'mas'.
'practically' means to remove the last letter.
'divine' becomes 'sacred' (similar in meaning).
'sacred' with its final letter taken away is 'sacre'.
'mas'+'sacre'='MASSACRE'
(Other definitions for massacre that I've seen before include "Murder (of many persons)" , "Indiscriminate slaughter" , "Complete defeat" , "Wholesale slaughter" , "Mass murder" .)