Charming parent stuck with Aunt Ethel every so often (9,2)

I believe the answer is:

buttering up

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'charming' is the definition.
The answer and definition can be both to do with communicating as well as being present participle verbs.
Perhaps you can see a link between them that I can't see?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Another definition for buttering up that I've seen is " Wheedling".)

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