Fossil fuel, Rishi's confessed addiction (4)
I believe the answer is:
coke
'fossil fuel' is the definition.
'coke' can be an answer for 'fuel' (coke is a kind of fuel). I'm not certain of the 'fossil' bit.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for coke that I've seen before include "A solid fuel; a drug (abbr.)" , "Drink - drug - solid-fuel product" , "Substance left after gas and tar have been extracted from coal" , "Drug (abbr) - soft drink (abbr)" , "Fuel made from coal" .)