Upper classes at home with the liqueur (8)

I believe the answer is:

absinthe

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'liqueur' is the definition.
(absinthe is a kind of liqueur)

'upper classes at home with the' is the wordplay.
'upper classes' becomes 'abs' (I can't justify this - if you can you should believe this answer much more).
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'with' says to put letters next to each other.
'abs'+'in'+'the'='ABSINTHE'

Can you help me to learn more?

(Other definitions for absinthe that I've seen before include "Aniseed-flavoured liqueur" , "Bathes in strong liquour, strangely" , "Green wormwood drink" , "Potent green gin-type liquor - wormwood" , "intoxicant" .)

I've seen this clue in The Guardian.

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