Race fairly, gain evenly (5)
I believe the answer is:
aryan
'race' is the definition.
(old-fashioned racial category)
'fairly gain evenly' is the wordplay.
'evenly' indicates alternate letters (the letters in even-numbered positions).
'fairly'+'gain'='fairlygain'
The alternating letters of 'fairlygain' are 'ARYAN'.
(Other definitions for aryan that I've seen before include "Ancient language" , "Denoting Caucasian origin, in Nazi ideology" , "One of an ancient people" , "Early Indo-European language" , "Of hte Indo-European language family" .)