Controversy in prison (4)
I believe the answer is:
stir
I believe this clue is a double definition.
'controversy' is the first definition.
(as in causing a stir)
'prison' is the second definition.
(informal term for prison)
'in' is the link.
(Other definitions for stir that I've seen before include "Stimulate; prison" , "Agitate, arouse" , "Whisk or whip" , "riot" , "Move around - prison" .)