Bill promises to pay after repair, being dishonest (10)
I believe the answer is:
mendacious
'dishonest' is the definition.
('mendacious' can be a synonym of 'dishonest')
'bill promises to pay after repair' is the wordplay.
'bill' becomes 'ac'.
'promises to pay' becomes 'ious' (more than one iou).
'after' says to put letters next to each other.
'repair' becomes 'mend' ('mend' can be a synonym of 'repair').
'ac'+'ious'='acious'
'acious' put after 'mend' is 'MENDACIOUS'.
'being' is the link.
(Other definitions for mendacious that I've seen before include "Untruthful" , "falsifying accounts?" , "Given to lying" .)