Head of sport leaving great magazine (5)
I believe the answer is:
comic
'magazine' is the definition.
(comic is a kind of magazine)
I cannot understand how the remainder of the clue works.
(Other definitions for comic that I've seen before include "Professional joke-teller" , "Funny, laughable" , "Comedian - humorous - children''s magazine" , "Professional funny person" , "Amusing, laughable" .)