One's served porridge, perhaps (8)
I believe the answer is:
sentence
I believe this clue is a double definition.
'one's served' is the first definition.
(a prison sentence is served)
'porridge perhaps' is the second definition.
(porridge can mean a prison sentence)
(Other definitions for sentence that I've seen before include "Group of words with verb" , "Written" , "Pass judgement on" , "Court decision on a grammatical structure" , "Unit of writing" .)