Bill after Elizabeth (6)
I believe the answer is:
poster
'bill' is the definition.
('poster' can be a synonym of 'bill')
'after elizabeth' is the wordplay.
'after' becomes 'post' (I've seen this before).
'elizabeth' becomes 'er'.
'post'+'er'='POSTER'
(Other definitions for poster that I've seen before include "Large decorative printed picture" , "Large printed bill" , "Bill or placard" , "Large sheet of paper advertising something" , "bulletin board participant" .)