Blue-green beverage left (4)
I believe the answer is:
teal
'blue-green' is the definition.
(I know that blue-green can be written as teal)
'beverage left' is the wordplay.
'beverage' becomes 'tea' (tea is a kind of beverage).
'left' becomes 'l' (common abbreviation).
'tea'+'l'='TEAL'
(Other definitions for teal that I've seen before include "Bluish shade of green" , "Small, short-necked duck" , "Variety of small ducks" , "Small river duck" , "Duck; greenish-blue colour" .)