Wild Bill's after Mike (3)
I believe the answer is:
mad
'wild' is the definition.
('mad' can be similar in meaning to 'wild')
'bill's after mike' is the wordplay.
'bill' becomes 'ad' (advertisement stuck on wall**).
'after' says to put letters next to each other.
'mike' becomes 'm' (phonetic alphabet: alpha, bravo, charlie etc.).
'ad' after 'm' is 'MAD'.
(Other definitions for mad that I've seen before include "Frantic" , "Idiotic" , "Demented or excited or angry" , "Angry or insane" , "Crackers" .)