The most common and most likely answer to this crossword clue is the 3 letter word GAS
I've seen this crossword clue in The Times
G
A
S
More clues leading to the result GAS
Buddy explains!
The straight part
We know that "fossil fuel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fossil fuel = gas.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 GAS mean?
GAS noun- Matter in a state intermediate between liquid and plasma that can be contained only if it is fully surrounded by a solid (or in a bubble of liquid) (or held together by gravitational pull); it can condense into a liquid, or can (rarely) become a solid directly.
- A chemical element or compound in such a state.
- A flammable gaseous hydrocarbon or hydrocarbon mixture (typically predominantly methane) used as a fuel, e.g. for cooking, heating, electricity generation or as a fuel in internal combustion engines in vehicles.
- A hob on a gas cooker.
- Methane or other waste gases trapped in one's belly as a result of the digestive process.
- A humorous or entertaining event or person.
- Frothy talk; chatter.
- A fastball.
- Arterial or venous blood gas.
- Marijuana, typically of high quality.
- To kill with poisonous gas.
- To talk in a boastful or vapid way; chatter.
- To impose upon by talking boastfully.
- To emit gas.
- To impregnate with gas.
- To singe, as in a gas flame, so as to remove loose fibers.
- Gasoline; a derivative of petroleum used as fuel.
- Gas pedal.
- To give a vehicle more fuel in order to accelerate it.
- To fill (a vehicle's fuel tank) with fuel.
- Comical, zany; fun, amusing