Prison resistance? It’s over (4)
I believe the answer is:
stir
'prison' is the definition.
(informal term for prison)
'resistance? it's over' is the wordplay.
'resistance?' becomes 'r' (abbreviation).
'over' shows that the letters should be reversed in order.
'r'+'its'='rits'
'rits' written backwards gives 'STIR'.
(Other definitions for stir that I've seen before include "Create revolutionary movement" , "Arouse (a memory)" , "Disturb" , "Rotate spoon" , "Mix the ingredients" .)