Drink firms on either side of America (5)
I believe the answer is:
cocoa
'drink' is the definition.
(cocoa is a kind of drink)
'firms on either side of america' is the wordplay.
'firms on either side of' becomes 'coco' (I am not sure about this - if you are sure you should believe this answer much more).
'america' becomes 'a' (common abbreviation - e.g. in organisation names).
'coco'+'a'='COCOA'
Can you help me to learn more?
(Other definitions for cocoa that I've seen before include "Reddish brown" , "Chocolate-like drink" , "Milky hot drink" , "Nighttime drink" , "product of beans!" .)