They include a study of Greek races (8)
I believe the answer is:
classics
'study of greek races' is the definition.
'classics' can be an answer for 'study' (classics is a kind of study). I am not certain of the 'of greek races' bit.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for classics that I've seen before include "Greek and Latin studies" , "number of races" , "great literary works" , "Established works of literature" , "Long established and enduring works of art" .)