Firm can set out to restrict debt (9)
I believe the answer is:
tenacious
'firm' is the definition.
(thesaurus)
'can set out to restrict debt' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'to restrict' is an insertion indicator.
'debt' becomes 'iou'.
'can'+'set'='canset'
'canset' anagrammed gives 'tenacs'.
'tenacs' enclosing 'iou' is 'TENACIOUS'.
(Other definitions for tenacious that I've seen before include "Persistent in holding on" , "Dogged" , "Holding fast" , "refusing to give up" , "Persevering" .)