Happy with evidence of debts? That's controversial (11)
I believe the answer is:
contentious
'controversial' is the definition.
(I've seen this before)
'happy with evidence of debts?' is the wordplay.
'happy' becomes 'content' (associated in meaning).
'with' says to put letters next to each other.
'evidence of debts?' becomes 'IOUs' (IOU's or I Owe You's).
'content'+'ious'='CONTENTIOUS'
'that's' is the link.
(Other definitions for contentious that I've seen before include "Likely to cause an argument" , "Likely to cause disagreement" , "debatable" , "controversial" .)