Greek sun god (6)
I believe the answer is:
apollo
'greek sun god' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for apollo that I've seen before include "source of name for far-flung missions" , "American space programme for landing men on moon" , "Greek god of the sun (6)" , "US space program" , "Handsome young man of Greek mythology" .)