Insightful tale about debts (9)
I believe the answer is:
sagacious
'insightful' is the definition.
(thesaurus)
'tale about debts' is the wordplay.
'tale' becomes 'saga' (I've seen this in another clue).
'about' becomes 'c' (abbreviation for 'circa').
'debts' becomes 'IOUs' (promises to pay debts).
'saga'+'c'+'ious'='SAGACIOUS'
(Other definitions for sagacious that I've seen before include "Wise" , "Astute" .)