Bookish boss with evidence of debts (8)
I believe the answer is:
studious
'bookish' is the definition.
('studious' can be a synonym of 'bookish')
'boss with evidence of debts' is the wordplay.
'boss' becomes 'stud' ('stud' can be a synonym of 'boss').
'with' says to put letters next to each other.
'evidence of debts' becomes 'ious' (I've seen this in other clues).
'stud'+'ious'='STUDIOUS'
(Other definitions for studious that I've seen before include "Diligent; scholarly" , "showing diligence" , "Bookish, scholarly" , "Thoughtful - hard-working" , "reading a lot" .)