Military duke, having lost wife, becomes a composer (9)

I believe the answer is:

ellington

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'military duke' is the definition.
'ellington' can be an answer for 'duke' (I've seen this before). I am not sure about the 'military' bit.

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for ellington that I've seen before include "One Duke" , "Musician" , "Duke --, twentieth century band leader" , "Duke - (Mood Indigo)" , "Duke (of jazz)" .)

I've seen this clue in The Irish Times.

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