Frank's in prison, having cheated (6)
I believe the answer is:
candid
'frank's' is the definition.
(synonyms)
'prison having cheated' is the wordplay.
'prison' becomes 'can' (the can is American slang for prison).
'having' is a charade indicator (letters next to each other).
'cheated' becomes 'did' (do can mean to cheat or trick).
'can'+'did'='CANDID'
'in' is the link.
(Other definitions for candid that I've seen before include "Truthful and straightforward" , "Impartial" , "Frank and outspoken" , "Very clear" , "Frank, honest" .)