Extremely generous one? (3)

I believe the answer is:

tip

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'extremely generous one?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

This is all the clue.

Can you help me to learn more?

(Other definitions for tip that I've seen before include "The rubbish dump" , "Hint, suggestion" , "Useful suggestion" , "present!" , "Pointed extremity" .)

I've seen this clue in the Evening Standard.

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