Prison commotion (4)
I believe the answer is:
stir
I believe this clue is a double definition.
'prison' is the first definition.
(informal term for prison)
'commotion' is the second definition.
(stir can mean a commotion)
(Other definitions for stir that I've seen before include "Mix the ingredients" , "Create revolutionary movement" , "Sensation" , "Prison - mix" , "Move around - prison" .)