Bird-dog gets drunk (8)
I believe the answer is:
cocktail
'drunk' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'bird-dog' is the wordplay.
'bird' becomes 'cock' (cock is a kind of bird).
'dog' becomes 'tail' (synonyms).
'cock'+'tail'='COCKTAIL'
'gets' acts as a link.
Can you help me to learn more?
(Other definitions for cocktail that I've seen before include "Possibly old-fashioned" , "Mixed beverage" , "snowball?" , "Manhattan, for example" , "old-fashioned in America" .)