To encourage debts is false (8)
I believe the answer is:
spurious
'is false' is the definition.
(I've seen this before)
'to encourage debts' is the wordplay.
'to encourage' becomes 'spur' (spur can mean to encourage).
'debts' becomes 'IOUs' (promises to pay debts).
'spur'+'ious'='SPURIOUS'
(Other definitions for spurious that I've seen before include "Not genuine or authentic" , "Plausible, but false" , "Contrived" , "Artificial and phoney" , "Forged" .)