Cooler sensation (4)
I believe the answer is:
stir
This clue is a double definition.
'cooler' is the first definition.
(both are slang terms for prison)
'sensation' is the second definition.
(I've seen this before)
(Other definitions for stir that I've seen before include "Thrill" , "Cause trouble" , "Excite emotionally" , "Wake up - prison" , "Slight movement" .)