Cocktail served in a tall glass (8)
I believe the answer is:
highball
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">cocktail served in a tall glass</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for highball that I've seen before include "speed?" , "Whisky and soda with ice" , "Mixed drink served in a tall glass" , "Beverage" , "Iced alcoholic drink in tall glass" .)