Whisky cocktail perhaps disagreeable (4)
I believe the answer is:
sour
This clue is a double definition.
'whisky cocktail perhaps' is the first definition.
(whisky sour is a cocktail)
'disagreeable' is the second definition.
(thesaurus)
(Other definitions for sour that I've seen before include "Rancid or tart" , "Curdled" , "Disparagement of something one can't have oneself" , "Sharp- or tart-tasting" , "Having an acidic taste" .)