Bill to demand approval (7)
I believe the answer is:
acclaim
'approval' is the definition.
(acclaim is a kind of approval)
'bill to demand' is the wordplay.
'bill' becomes 'ac'.
'to demand' becomes 'claim' (claiming is a kind of demanding).
'ac'+'claim'='ACCLAIM'
(Other definitions for acclaim that I've seen before include "Extol" , "Salute, applaud" , "commendation" , "Enthusiastic approval" , "Declare" .)