Crowding a great multitude in note (9)

I believe the answer is:

thronging

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

'crowding' is the definition.
(thronging is a kind of crowding)

'a great multitude in note' is the wordplay.
I cannot really understand how this works, but
'great' could be 'g' (abbreviation in place names) and 'g' is located in the answer.
'in' is present in the answer.
'multitude' could be 'throng' (synonyms) and 'throng' is found within the answer.
No letters remain.
This explanation may well be incorrect...

Can you help me to learn more?

(Another definition for thronging that I've seen is " Pressing".)

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

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