Crossword Genius

How a witness appears to Noah in disguise (2,4)

Ross

I believe the answer is:

on oath

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'how a witness' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'to noah in disguise' is the wordplay.
'in disguise' is an anagram indicator.
'to'+'noah'='tonoah'
'tonoah' is an anagram of 'ON OATH'.

'appears' acts as a link.

Can you help me to learn more?

(Other definitions for on oath that I've seen before include "Bound to speak the truth" , "Sworn to speak the truth" .)

I've seen this clue in The Globe and Mail.
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