Sly, trendy man with evidence of debts (9)
I believe the answer is:
insidious
'sly' is the definition.
(thesaurus)
'trendy man with evidence of debts' is the wordplay.
'trendy' becomes 'in'.
'man' becomes 'sid' (**).
'with' is a charade indicator (letters next to each other).
'evidence of debts' becomes 'ious' (I've seen this in other clues).
'in'+'sid'+'ious'='INSIDIOUS'
(Other definitions for insidious that I've seen before include "Gradually harmful" , "Slowly having a harmful effect" , "Treacherous; subtle" , "Proceeding subtly but harmfully" , "crafty" .)