Are they fools to throng together? (5,5)

I believe the answer is:

dense crowd

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'together?' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'are they fools to throng' is the wordplay.
'are they fools' becomes 'dense' (I can't justify this - if you can you should give a lot more credence to this answer).
'to throng' becomes 'crowd' (I've seen this before).
'dense'+'crowd'='DENSE CROWD'

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