Notice of proposed legislation (4)
I believe the answer is:
bill
I believe this clue is a double definition.
'notice' is the first definition.
(both can mean an advertisement)
'proposed legislation' is the second definition.
'of' acts as a link.
(Other definitions for bill that I've seen before include "Poster; draft law" , "informing of damage" , "beak demanded" , "Little William" , "Banknote; beak" .)