He's back from Vietnam (3)

I believe the answer is:

man

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'he's' is the definition.
(I've seen this in another clue)

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

(Other definitions for man that I've seen before include "Isle of ..., ... o'war" , "Irish Sea isle" , "Geezer" , "Male person" , "Valet" .)

I've seen this clue in the Evening Standard.

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