Vacuous bunch of developers could use such a site (6,3)

I believe the answer is:

vacant lot

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'developers could use such a site' is the definition.
I can't judge whether this defines the answer.

'vacuous bunch' is the wordplay.
'vacuous' becomes 'vacant' (I can't justify this - if you can you should believe this answer much more).
'bunch' becomes 'lot' (synonyms).
'vacant'+'lot'='VACANT LOT'

'of' acts as a link.

Can you help me to learn more?

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

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