Rewritten his parts? The copy for nervous disorder specialist? (15)

I believe the answer is:

psychotherapist

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

'nervous disorder specialist?' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

'rewritten his parts? the copy' is the wordplay.
'rewritten' indicates an anagram.
'his'+'parts'+'the'+'copy'='hispartsthecopy'
'hispartsthecopy' with letters rearranged gives 'PSYCHOTHERAPIST'.

'for' acts as a link.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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