Style of frying in a jug? (4)
I believe the answer is:
stir
'a jug?' is the definition.
(both are slang for prison)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for stir that I've seen before include "Prison (sl.); agitate" , "Agitate; wake from sleep" , "Arouse; mix" , "Big house" , "Commotion to mix" .)