Certainly not the best of spirits! (5)

I believe the answer is:

ghoul

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'best of spirits' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?

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

Can you help me to learn more?

(Other definitions for ghoul that I've seen before include "shade" , "Morbid voyeur" , "Morbid type" , "Macabre fiend" , "Evil presence" .)

I've seen this clue in the Evening Standard.

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