Postponing one's leave (7)

I believe the answer is:

staying

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'postponing' is the definition.
The answer and definition can be both to do with fundamental existence as well as being present participle verbs.
Maybe you can see an association between them that I can't see?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Another definition for staying that I've seen is " Remaining in the same place".)

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

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