Son leaving girl to become fighter (3)

I believe the answer is:

ali

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'fighter' is the definition.
(I have seen 'Old fighter' mean 'ali' so perhaps 'fighter' could also mean 'ali')

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

Can you help me to learn more?

(Other definitions for ali that I've seen before include "Dickens novel" , "Muhammad or Baba?" , "Cassius Clay became Muhammad ..." , "Muhammad - - , legendary boxer" , "Egyptian name" .)

I've seen this clue in The Independent.

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