Winning American crown (5)
I believe the answer is:
ahead
'winning' is the definition.
(both can mean in the lead)
'american crown' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'crown' becomes 'head' ().
'a'+'head'='AHEAD'
(Other definitions for ahead that I've seen before include "In the vanguard" , "In the future" , "Winning" , "What's down the road" , "Forwards" .)