Drink mother's ruin — are legs almost buckling? (6,3)
I believe the answer is:
ginger ale
'drink' is the definition.
(ginger ale is a kind of drink)
'mother's ruin are legs almost buckling?' is the wordplay.
'mother's ruin' becomes 'gin' (informal term for gin).
'almost' means to remove the last letter (most of the word but not all of it).
'buckling?' indicates an anagram (I've seen 'buckle' mean this).
'are'+'legs'='arelegs'
'arelegs' with its last letter taken away is 'areleg'.
'areleg' anagrammed gives 'gerale'.
'gin'+'gerale'='GINGER ALE'
(Other definitions for ginger ale that I've seen before include "One drink" , "pop" , "It won't make you drunk!" , "Fizzy drink" , "Spicy, sweetened non-alcoholic drink" .)