Possible Clues:

• Maureen's first among arrivals to imbibe one's Buck's fizz
• Graduate welcomes tips in making one sparkling champagne cocktail
• Shrub found in Michigan, Missouri and South America?
• Bubbly brunch beverage
• Flowering tree found in Maoism
• Flower; Buck's fizz
• Old woman has grabbed one’s abnormally large shrub
• Boozy brunch order
• One may be "bottomless" at brunch
• Maoism (anag)