Culmination, climax (6)
I believe the answer is:
apogee
I believe this clue is a double definition.
'culmination' is the first definition.
(synonyms)
'climax' is the second definition.
(I've seen this in another clue)
(Other definitions for apogee that I've seen before include "Highest point (of orbit)" , "Culmination, climax" , "crown" , "Point in the orbit of the moon that's furthest from the earth" , "Highest or most distant point, or climax" .)