Plan Nietzsche managed to keep under wraps (6)

I believe the answer is:

schema

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'plan nietzsche managed to keep under wraps' is the definition.
I can't judge whether this defines the answer.

'plan nietzsche managed to keep' is the wordplay.
'to keep' says the answer is hidden in the clue.
'SCHEMA' is hidden within 'plan nietzsche managed'.

Can you help me to learn more?

(Other definitions for schema that I've seen before include "Outline or model of a technical plan or theory" , "Synopsis" , "essential form" , "Outline plan or theory - he's Mac (anag)" , "Proposed arrangement" .)

I've seen this clue in The Independent.

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