Knowing just what you have in mind (10)

I believe the answer is:

telepathic

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'knowing' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I can't see?

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

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(Other definitions for telepathic that I've seen before include "Able to pick up ideas" , "Extraordinarily communicative" , "Clairvoyant" , "Mind-reading" , "Communicating by mind alone" .)

I've seen this clue in the Evening Standard.

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