Mum noisily prepares breakfast? (9)

I believe the answer is:

shreddies

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

'noisily prepares breakfast?' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'mum' is the wordplay.
I cannot quite see how this works, but
'mum' could be 'sh' (both can be used to tell someone to be quiet) and 'sh' is found within the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in The Independent.

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