Lager drunk after spirit, drinker's penultimate drink (6,3)
I believe the answer is:
Here is my best explanation:
'drink' is the definition.
(ginger ale is a kind of drink)
'lager drunk after spirit drinker's penultimate' is the subsidiary indication.
'drunk' indicates an anagram.
'after' means one lot of letters go next to another.
'spirit' becomes 'gin' (I've seen this before).
'drinker's penultimate' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'lager' with letters rearranged gives 'geral'.
'geral' put after 'gin' is 'gingeral'.
(Other definitions for ginger ale that I've seen before include "It won't make you drunk!", "Drink", "Fizzy drink", "pop", "One drink" and "Spicy, sweetened non-alcoholic drink".)