Top evidence initially disregarded (4)

I believe the answer is:

roof

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'top evidence initially disregarded' is the definition.
I can't tell whether this definition defines the answer.

'top evidence' is the wordplay.
'top' means to remove the first letter.
'evidence' becomes 'proof' (evidence proves something).
'proof' with its first letter taken away is 'ROOF'.

Can you help me to learn more?

(Other definitions for roof that I've seen before include "Part of mouth" , "Top of car/house" , "House's top" , "Covering of house" , "Protective covering on top" .)

I've seen this clue in The Guardian.

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