Brunch cocktail (6)
I believe the answer is:
mimosa
'brunch cocktail' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mimosa that I've seen before include "Australian 15 across" , "Tree with scented clustered flowers" , "Tropical tree or shrub with clusters of fragrant flowers" , "Plant genus popularly extended to the Acacia" , "Tropical shrub with yellow flowers" .)