Crossword Genius

Making a grade one drink (9)

Ross

I believe the answer is:

orangeade

'drink' is the definition.
(orangeade is a kind of drink)

'making a grade one' is the wordplay.
'making' is an anagram indicator.
'a'+'grade'+'one'='agradeone'
'agradeone' with letters rearranged gives 'ORANGEADE'.

(Other definitions for orangeade that I've seen before include "Fruit drink", "Squash", "Bubbly drink", "Pop", "Fruity drink".)