Agreeing the bill's binding (9)
I believe the answer is:
according
'agreeing' is the definition.
(according is a kind of agreeing)
'the bill's binding' is the wordplay.
'the bill' becomes 'ac'.
'binding' becomes 'cording' (cording is a kind of binding).
'ac'+'cording'='ACCORDING'
(Other definitions for according that I've seen before include "Allotting or granting" , "As reported or stated by" .)