Moon mission (6)
I believe the answer is:
apollo
'moon mission' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for apollo that I've seen before include "Handsome Greek god" , "London theatre" , "Greek god; large European butterfly" , "God of light and US space programme" , "Greek god of light, poetry, music, healing and prophecy" .)