Moving article on prison (5)
I believe the answer is:
astir
'moving' is the definition.
(I've seen this before)
'article on prison' is the wordplay.
'article' becomes 'a' (indefinite article).
'on' says to put letters next to each other.
'prison' becomes 'stir' (informal term for prison).
'a'+'stir'='ASTIR'
(Other definitions for astir that I've seen before include "In motion - out of bed" , "abroad" , "This isn't still" , "Excitedly moving" , "Awake and out of bed" .)