Posh car with new instrument serving drink (10)

I believe the answer is:

limoncello

'drink' is the definition.
(type of liqueur)

'posh car with new instrument' is the wordplay.
'posh car' becomes 'limo' (short for limousine).
'with' says to put letters next to each other.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'instrument' becomes 'cello' (cello is a kind of instrument).
'limo'+'n'+'cello'='LIMONCELLO'

'serving' acts as a link.

I've seen this clue in The Guardian.

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