Leading poster about male article (5)
I believe the answer is:
ahead
'leading' is the definition.
(to lead is to go ahead)
'poster about male article' is the wordplay.
'poster' becomes 'ad' (short for advert).
'about' is an insertion indicator.
'male' becomes 'he' (he refers to a man).
'article' becomes 'a' (the indefinite article in English).
'he'+'a'='hea'
'ad' enclosing 'hea' is 'AHEAD'.
(Other definitions for ahead that I've seen before include "advanced" , "In the leading position" , "Forward - in front" , "Forwards" , "In front as in race" .)