Up and about in a prison (5)
I believe the answer is:
astir
'up and about' is the definition.
(I've seen this before)
'a prison' is the wordplay.
'prison' becomes 'stir' (informal term for prison).
'a'+'stir'='ASTIR'
'in' acts as a link.
(Other definitions for astir that I've seen before include "Awake and out of bed" , "Out of bed or on the move" , "Moving; out of bed" , "Up and about -- is art (anag)" , "abroad" .)