NASA's lunar program (6)
I believe the answer is:
apollo
'nasa's lunar program' 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 "Greek god of light, son of Zeus" , "US spacecraft" , "US space flight programme, 1961-72" , "Greek sun god and leader of the Muses" , "Handsome young man of Greek mythology" .)