Had made the grade, one understood (8)

I believe the answer is:

gathered

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'one understood' is the definition.
(I've seen this before)

'had made the grade' is the wordplay.
'the grade' can be anagrammed to 'GATHERED'.
But, I am not clear how this is indicated.

Can you help me to learn more?

(Other definitions for gathered that I've seen before include "Surmised" , "Collected - inferred" , "Got together - tucked in" , "Picked up" , "assumed" .)

I've seen this clue in the Evening Standard.

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