Heartily affable and extremely nice (3)

I believe the answer is:

fab

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'extremely nice' is the definition.
I can't tell whether this definition defines the answer.

'heartily affable and' is the wordplay.
'heartily' indicates a hidden word (letters at the heart of the clue).
'FAB' can be found hidden inside 'affable and'.

Can you help me to learn more?

(Other definitions for fab that I've seen before include "Excellent (slang)" , "Marvellous (sl.)" .)

I've seen this clue in the Evening Standard.

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