Unendingly obey a power above, a god (6)
I believe the answer is:
apollo
'a god' is the definition.
(Apollo is a Greek god)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for apollo that I've seen before include "Greek (and Roman) god of light, poetry etc" , "Greek sun god and leader of the Muses" , "handsome youth" , "US spacecraft" , "Greek god; large European butterfly" .)