Prejudice regarding ethnicity (6)
I believe the answer is:
racism
'prejudice regarding ethnicity' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for racism that I've seen before include "Ethnic prejudice" , "Prejudice against people of other countries or nationalities" , "Prejudiced behaviour -- Sir Mac (anag)" , "Form of discrimination" , "A basis for hate crime" .)