Commit prisoner on notice (7)
I believe the answer is:
consign
'commit' is the definition.
(consigning is a kind of commiting)
'prisoner on notice' is the wordplay.
'prisoner' becomes 'con' (abbreviation for 'convict').
'on' says to put letters next to each other.
'notice' becomes 'sign' (I've seen this before**).
'con'+'sign'='CONSIGN'
(Other definitions for consign that I've seen before include "Deliver (to someone's custody)" , "dispatch" , "Give over for safekeeping" , "Give over to another" , "Commit or deliver formally" .)