Bitterness in cognac I drank (4)

I believe the answer is:

acid

'bitterness' is the definition.
(thesaurus)

'in cognac i drank' is the wordplay.
'in' says the answer is hidden in the clue.
'ACID' can be found hidden inside 'cognac i drank'.

(Other definitions for acid that I've seen before include "It turns litmus paper red" , "Bitter; biting" , "Sour - LSD" , "Sour (substance)" , "Caustic liquid of many kinds" .)

I've seen this clue in The Mirror.

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