It takes a long time to change one (3)

I believe the answer is:

eon

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'it takes a long time' is the definition.
The definition suggests a singular noun which matches the answer.

'change one' is the wordplay.
'change' indicates anagramming the letters.
'one' with letters rearranged gives 'EON'.

'to' is the link.

Can you help me to learn more?

(Other definitions for eon that I've seen before include "Geological period" , "Huge time period" , "An immense time" , "Prolonged period" , "Immense period" .)

I've seen this clue in the Evening Standard.

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