One too shrewd to take sour grapes (3)

I believe the answer is:

fox

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'sour grapes' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for fox that I've seen before include "Baffle; mammal" , "Sly type" , "Trick" , "Cunning animal" , "Animal; to cheat" .)

I've seen this clue in the Evening Standard.

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