Relating to ethnicity (6)
I believe the answer is:
racial
'relating to ethnicity' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for racial that I've seen before include "Relating to ethnic group" , "Relating to ethnicity" , "Relating to ethnic divisions" , "Of particular people or colour, as with prejudice" , "on coloured lines?" .)