Only punishment feared by the prisoner? (8)
I believe the answer is:
solitary
'only' is the definition.
(I know that only can be written as solitary)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for solitary that I've seen before include "Existing alone" , "Alone, single" , "punishment" , "friendless" , "not a Companion" .)