What an engine may consume in overdrive, possibly? (4)
I believe the answer is:
derv
'overdrive possibly?' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for derv that I've seen before include "Vehicle fuel oil" , "Type of fuel" , "Water monster" , "Vehicle diesel-oil" , "Diesel engine fuel oil" .)