Standard garment possibly made by prisoners (6)
I believe the answer is:
escape
'standard garment possibly made by prisoners' is the definition.
I can't judge whether this defines the answer.
'standard garment' is the wordplay.
'standard' becomes 'es' (I am not sure about this - if you are sure you should believe this answer much more).
'garment' becomes 'cape' (cape is a kind of garment).
'es'+'cape'='ESCAPE'
Can you help me to learn more?
(Other definitions for escape that I've seen before include "Get out of captivity, go over the wall" , "Abscond, flee" , "Get away from captivity" , "Gain freedom" , "See cap (anag.)" .)