Making a grade one drink (9)
'drink' is the definition.
(orangeade is a kind of drink)
'making a grade one' is the wordplay.
'making' is an anagram indicator.
'agradeone' with letters rearranged gives 'ORANGEADE'.
(Other definitions for orangeade that I've seen before include "Fruit drink", "Squash", "Bubbly drink", "Pop", "Fruity drink".)