Huge waste cutting fossil fuel (8)
I believe the answer is:
colossal
'huge' is the definition.
(I know that huge can be written as colossal)
'waste cutting fossil fuel' is the wordplay.
'waste' becomes 'loss' (I can't justify this - if you can you should believe this answer much more).
'cutting' indicates putting letters inside (some letters cut their way into a word).
'fossil fuel' becomes 'coal' (coal is a kind of fossil fuel).
'loss' put into 'coal' is 'COLOSSAL'.
Can you help me to learn more?
(Other definitions for colossal that I've seen before include "Mammoth" , "Huge, immense" , "Enormous, gigantic" , "Giant" , "Great" .)