Start prison disturbance (4)
I believe the answer is:
stir
I believe this clue is a triple definition!
'start' is the first definition.
(both can mean to initiate or cause something)
'prison' is the second definition.
(informal term for prison)
'disturbance' is the third definition.
(synonyms)
(Other definitions for stir that I've seen before include "Arouse; commotion" , "Cause trouble" , "Big house" , "Wake; disturbance" , "Agitate; wake from sleep" .)