To Ann, he's a changed man (5)

I believe the answer is:

anton

I'm a little stuck... Click here to teach me more about this clue!

'man' is the definition.
(I've seen this before)

'to ann he's a changed' is the wordplay.
'to ann' anagrams to 'ANTON'.
However, I'm not clear how this is indicated.

Can you help me to learn more?

(Other definitions for anton that I've seen before include "Boy" , "-- Bruckner, composer" , "..... Chekov" , "Chekhov maybe" , "Chekhov, say" .)

I've seen this clue in the Evening Standard.

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