The most common and most likely answer to this crossword clue is the 8 letter word COLOSSAL
I've seen this crossword clue in The Times
C
O
L
O
S
S
A
L
More clues leading to the result COLOSSAL
- Tremendous destruction inside burner
- Vast financial deficit in output from colliery
- Deficit in fuel is massive
- Enormous deficiency in fossil fuel
- Huge detriment involved in fossil fuel
- Huge deficit in fossil fuel
- Massive column with rope around
- Extremely large reduction in fuel that’s consumed
- Enormous deficit in solid fuel
- Big drop into the black stuff
Buddy explains!

The straight part
We know that "Tremendous" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tremendous = colossal.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does COLOSSAL mean?
COLOSSAL adjective- Extremely large or on a great scale.