Collected ratbag Greg at educational centre (10)

I believe the answer is:

aggregated

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'collected' is the definition.

'ratbag greg at educational centre' is the wordplay.
'AGGREGATED' is hidden within the letters.
However, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for aggregated that I've seen before include "Combined into a whole" , "Made to go to mass" .)

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

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