Check prisoners learn with time (10)
I believe the answer is:
constraint
'check' is the definition.
(I've seen this before)
'prisoners learn with time' is the wordplay.
'prisoners' becomes 'cons' (short for convicts).
'learn' becomes 'train' (training is a kind of learning).
'with' is a charade indicator (letters next to each other).
'time' becomes 't' (abbreviation).
'cons'+'train'+'t'='CONSTRAINT'
(Other definitions for constraint that I've seen before include "force" , "restriction made" , "Check" , "Restriction - in contrast (anag)" , "restrictive condition" .)