Unfinished greenish-blue drink (3)
I believe the answer is:
tea
'drink' is the definition.
(tea is a drink)
'unfinished greenish-blue' is the wordplay.
'unfinished' means to remove the last letter.
'greenish-blue' becomes 'teal' (I've seen this before).
'teal' with its final letter removed is 'TEA'.
(Other definitions for tea that I've seen before include "Afternoon or evening meal" , "Meal/drink" , "Earl Grey?" , "TREE" , "Common drink" .)