Kay's evening drink? (8)
I believe the answer is:
cocktail
This could be a double definition.
'kay's' is the first definition.
Both the answer and definition are singular nouns.
Maybe you can see a link between them that I don't see?
'evening drink?' is the second definition.
(Other definitions for cocktail that I've seen before include "Possibly old-fashioned" , "snowball?" , "Mixed beverage" , "Harvey Wallbanger, for example" , "Manhattan, for example" .)