Not to close down at any time (5)

I believe the answer is:

never

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'not' is the definition.
(thesaurus)

'close down at any time' is the wordplay.
'close down at' becomes 'n' (I can't explain this - if you can you should believe this answer much more).
'any time' becomes 'ever' (I've seen this in another clue).
'n'+'ever'='NEVER'

'to' acts as a link.

Can you help me to learn more?

(Other definitions for never that I've seen before include "Strong negative" , "Do not give up!" , "Under no circumstances" , "Surely not" , "No way" .)

I've seen this clue in the Evening Standard.

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