Bills are revised by some politicians (8)
I believe the answer is:
liberals
'some politicians' is the definition.
(liberal is a type of politician)
'bills are revised' is the wordplay.
'revised' is an anagram indicator.
'bills'+'are'='billsare'
'billsare' with letters rearranged gives 'LIBERALS'.
'by' acts as a link.
(Other definitions for liberals that I've seen before include "Members of a British political party" , "They favour progress and reform" .)