Group turned up to flog a bit of mosaic (8)

I believe the answer is:

tessella

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

'group turned up to flog a' is the wordplay.
'group' becomes 'set' (both can mean a collection).
'turned up' is a reversal indicator.
'to flog' becomes 'sell' (I've seen this before).
'set' in reverse letter order is 'tes'.
'tes'+'sell'+'a'='TESSELLA'

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I've seen this clue in The Independent.

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