Escaping notice, you understand, in nun’s disguise (6)

I believe the answer is:

unseen

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'escaping notice you' is the definition.
I can't tell whether this definition defines the answer.

'understand in nun's disguise' is the wordplay.
'understand' becomes 'see' (synonyms).
'in' means one lot of letters goes inside another.
'disguise' is an anagram indicator (I've seen 'disguising' mean this).
'nun' is an anagram of 'unn'.
'see' placed into 'unn' is 'UNSEEN'.

Can you help me to learn more?

(Other definitions for unseen that I've seen before include "Concealed" , "Invisible or not observed" , "Not noticed" , "Translation exercise" , "Unobserved" .)

I've seen this clue in the Evening Standard.

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