American contest is concerning (5)
I believe the answer is:
about
'is concerning' is the definition.
(about can mean concerning or relating to)
'american contest' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'contest' becomes 'bout' (a bout is a boxing match).
'a'+'bout'='ABOUT'
(Other definitions for about that I've seen before include "Concerning; roughly" , "In conection with, all around" , "On the subject of, approximately" , "in action" , "in the offing?" .)