Cuba libre ingredient (4)
I believe the answer is:
coke
'cuba libre ingredient' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for coke that I've seen before include "Carbonised fuel residue" , "Fuel made from coal" , "Fuel derived from coal" , "Furnace fuel" , "Drink - drug - solid-fuel product" .)