Befuddled prisoner set up (10)
I believe the answer is:
confounded
'befuddled' is the definition.
(synonyms)
'prisoner set up' is the wordplay.
'prisoner' becomes 'con' (abbreviation for 'convict').
'set up' becomes 'founded' (I've seen this in other clues).
'con'+'founded'='CONFOUNDED'
(Other definitions for confounded that I've seen before include "Brought to confusion" , "ending of Te Deum?" , "Perplexed - damned" , "Really annoying (nuisance)" , "Confused; astonished" .)