Bill likely to change (5)
I believe the answer is:
adapt
'change' is the definition.
(adapting is a kind of changing)
'bill likely' is the wordplay.
'bill' becomes 'ad' (advertisement stuck on wall).
'likely' becomes 'apt' ('apt' can be similar in meaning to 'likely').
'ad'+'apt'='ADAPT'
'to' is the link.
(Other definitions for adapt that I've seen before include "Adjust (to new condition)" , "Modify, adjust" , "Accommodate" , "Acclimatize" , "Become adjusted to new conditions" .)