Bill receives armed conflict prize (5)
I believe the answer is:
award
'prize' is the definition.
('award' can be a synonym of 'prize')
'bill receives armed conflict' is the wordplay.
'bill' becomes 'ad' (advertisement stuck on wall).
'receives' means one lot of letters goes inside another.
'armed conflict' becomes 'war' (I've seen this before).
'ad' placed around 'war' is 'AWARD'.
(Other definitions for award that I've seen before include "medal, perhaps" , "Decoration" , "Tony is one" , "Tony, say" , "E.g. Oscar" .)