Agreed on a cocktail for drink (9)
I believe the answer is:
orangeade
'drink' is the definition.
(I've seen this before)
'agreed on a cocktail' is the wordplay.
'cocktail' indicates anagramming the letters.
'agreed'+'on'+'a'='agreedona'
'agreedona' is an anagram of 'ORANGEADE'.
'for' acts as a link.
(Other definitions for orangeade that I've seen before include "Fruit drink" , "Squash" , "Soft citrus drink" , "Pop" , "Bubbly drink" .)