Accept prisoner has finished (7)
I believe the answer is:
condone
'accept' is the definition.
(thesaurus)
'prisoner has finished' is the wordplay.
'prisoner' becomes 'con' (abbreviation for 'convict').
'has' says to put letters next to each other.
'finished' becomes 'done' ('done' can be similar in meaning to 'finished').
'con'+'done'='CONDONE'
(Other definitions for condone that I've seen before include "Excuse made" , "Nod once (anag) -- make allowances for" , "Overlook intentionally" , "Reluctantly sanction" , "Overlook - forgive" .)