Foam in front of champion outside (7)
I believe the answer is:
surface
'outside' is the definition.
(thesaurus)
'foam in front of champion' is the wordplay.
'foam' becomes 'surf' (I've seen this before).
'in front of' is a charade indicator (letters next to each other).
'champion' becomes 'ace' (both can mean a person excelling at something).
'surf'+'ace'='SURFACE'
(Other definitions for surface that I've seen before include "get out of bed" , "In water, come to the top" , "Outside part" , "Come up for air" , "Upper limit of liquid" .)