Long-haired type with a beard produced part of magnum opus (3)

I believe the answer is:

gnu

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

'long-haired type with a beard' is the definition.
I can't judge whether this defines the answer.

'part of magnum opus' is the wordplay.
'part of' indicates a hidden word.
'GNU' is hidden within 'magnum opus'.

'produced' acts as a link.

Can you help me to learn more?

(Other definitions for gnu that I've seen before include "Strange gun for an antelope" , "Literally wild beast" , "animals" , "Large African antelope" , "Large heavy antelope" .)

I've seen this clue in The Irish Times.

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