A number fell turning corner (4)

I believe the answer is:

nook

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'corner' is the definition.
(I know this)

'a number fell turning' is the wordplay.
'a number' becomes 'no' (abbreviation for 'number').
'fell turning' becomes 'ok' (I can't justify this - if you can you should believe this answer much more).
'no'+'ok'='NOOK'

Can you help me to learn more?

(Other definitions for nook that I've seen before include "Secluded spot" , "Cranny or niche" , "Secluded recess" , "Recess offering seclusion" , "Hidey-hole" .)

I've seen this clue in The Daily Mail.

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