Ethnicity contest (4)
I believe the answer is:
race
This clue is a double definition.
'ethnicity' is the first definition.
(I've seen this in another clue)
'contest' is the second definition.
(I know that race is a type of sports competition)
(Other definitions for race that I've seen before include "People; dash" , "descent" , "Contest; nation" , "People - sprint - competition" , "Run; nation" .)