Jointly composed by Angus, maybe, and English composer after intro (9)

I believe the answer is:

cowritten

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'angus maybe and english composer after intro' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'jointly composed' is the wordplay.
'jointly' becomes 'co' (I can't justify this - if you can you should give a lot more credence to this answer).
'composed' becomes 'written' ('write' can be a synonym of 'compose').
'co'+'written'='COWRITTEN'

'by' acts as a link.

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

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