Train me mending old clothes (7)

I believe the answer is:

raiment

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

'clothes' is the definition.
(raiment is a kind of clothes)

'train me mending old' is the wordplay.
'train me' can be anagrammed to 'RAIMENT'.
However, I'm not clear how this is indicated.

Can you help me to learn more?

(Other definitions for raiment that I've seen before include "Wear" , "investment" , "Old word for fine clothing" , "these garments are old-fashioned" , "Poetic word for clothing" .)

I've seen this clue in The Telegraph.

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