Being essentially selective, taste and sip Italian drink (4)

I believe the answer is:

asti

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'drink' is the definition.
(Asti is a type of wine)

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

(Other definitions for asti that I've seen before include "Sparkling wine named after an Italian Piedmont town" , "It's a (anag) - wine" , "Alcohol" , "Italian wine - (then change a letter for ...)" , "Source of fizz" .)

I've seen this clue in The Independent.

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