Cost was halved, then doubled, over a drink (5)
I believe the answer is:
cocoa
'drink' is the definition.
(I know that cocoa is a drink)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for cocoa that I've seen before include "Popular chocolate drink" , "Chocolate ingredient" , "Chocolate powder" , "Powder from cacao beans" , "Hot chocolate drink" .)