Prison unrest (4)
I believe the answer is:
stir
I believe this clue is a double definition.
'prison' is the first definition.
(informal term for prison)
'unrest' is the second definition.
(thesaurus)
(Other definitions for stir that I've seen before include "Prison (slang) - disturbance" , "unrest" , "Cause to move in slangy prison" , "Begin to move" , "Arouse; commotion" .)