American leader in front (5)
I believe the answer is:
ahead
'in front' is the definition.
(synonyms)
'american leader' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'leader' becomes 'head' (head is a kind of leader).
'a'+'head'='AHEAD'
(Other definitions for ahead that I've seen before include "In front as in race" , "in van" , "advanced" , "at pole" , "What's down the road" .)