Promote footballer (4)
I believe the answer is:
back
I believe this is a double definition.
'promote' is the first definition.
(thesaurus)
'footballer' is the second definition.
(back is a kind of footballer)
(Other definitions for back that I've seen before include "Stern" , "Fashionable again" , "Second" , "Place where secret deals are done" , "Support - football player" .)