Bewildered prisoner joined (8)
I believe the answer is:
confused
'bewildered' is the definition.
('confuse' can be a synonym of 'bewilder')
'prisoner joined' is the wordplay.
'prisoner' becomes 'con' (abbreviation for 'convict').
'joined' becomes 'fused' (I've seen this before).
'con'+'fused'='CONFUSED'
(Other definitions for confused that I've seen before include "Perplexed, befuddled" , "Muddled" , "Disorientated" , "Mixed up in fun codes" , "In a muddle, perplexed" .)