Rating or officer - destiny will reveal (7)
I believe the answer is:
matelot
'rating' is the definition.
(I've seen this before)
'officer destiny will reveal' is the wordplay.
I cannot quite understand how this works, but
'officer' could be 'mate' (mate is a kind of officer) and 'mate' is found within the answer.
'destiny' could be 'lot' (I've seen this in another clue) and 'lot' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'or' is the link.
Can you help me to learn more?
(Other definitions for matelot that I've seen before include "Rating" , "A lot met (anag) - sailor" , "One sailor" , "seafarer" , "One at sea" .)