Huntress mostly in race glowing (8)
I believe the answer is:
radiance
'glowing' is the definition.
(I know that glowing can be written as radiance)
'huntress mostly in race' is the wordplay.
'huntress' becomes 'Diana' (Greek hunter goddess).
'mostly' means to remove the last letter (most but not all of the word).
'in' means one lot of letters goes inside another.
'diana' with its final letter taken away is 'dian'.
'dian' inserted within 'race' is 'RADIANCE'.
(Other definitions for radiance that I've seen before include "Joyful splendour" , "Glowing quality" , "A bright glow (E, not Y)" , "Refulgence" , "moonlight" .)