The most common and most likely answer to this crossword clue is the 4 letter word DERV
I've seen this crossword clue in Financial Times
D
E
R
V
More clues leading to the result DERV
- Some order van fuel
- Fuel used in older vehicles
- Fuel that is partly undervalued
- Very embarrassed after upsetting contents of tank?
- Fuel used by older vans
- Fuel somewhat undervalued
- Fuel carried by wider vehicles
- Oddly dreary lead character from Vin Diesel
- Fuel stored in older vehicles
- Fuel taken from under vans
Buddy explains!

The straight part
We know that "Fuel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fuel = derv.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 DERV mean?
DERV noun- Diesel fuel for motor vehicles.