A repeated final winning move for the officer (6,4)
I believe the answer is:
'officer' is the definition.
(I have seen 'Naval officer' mean 'second mate' so perhaps 'officer' could also mean 'second mate')
'a repeated final winning move' is the wordplay.
'a repeated final' becomes 'second' (I am not sure about this - if you are sure you should believe this answer much more).
'winning move' becomes 'mate' (checkmate in chess).
'for the' acts as a link.
Can you help me to learn more?
(Other definitions for second mate that I've seen before include "Naval officer" , "one involved in bigamy?" , "Craftsman, perhaps" .)