Pardon prisoner executed (7)
I believe the answer is:
condone
'pardon' is the definition.
(both can mean to excuse wrongdoing)
'prisoner executed' is the wordplay.
'prisoner' becomes 'con' (abbreviation for 'convict').
'executed' becomes 'done' (execute can mean to do or accomplish).
'con'+'done'='CONDONE'
(Other definitions for condone that I've seen before include "Nod once (anag) -- make allowances for" , "Approve, sanction" , "Forgive, sanction" , "Overlook intentionally" , "pardon" .)