Isn't for one prisoner drawing (11)
I believe the answer is:
contraction
'isn't for one' is the definition.
('isn't' is a contraction of 'is not')
'prisoner drawing' is the wordplay.
'prisoner' becomes 'con' (abbreviation for 'convict').
'drawing' becomes 'traction' (process of drawing or dragging).
'con'+'traction'='CONTRACTION'
(Other definitions for contraction that I've seen before include "Process of size reduction" , "Isn't, for instance" .)