He uses a lot of fuel (6)
I believe the answer is:
stoker
'he uses a lot' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'fuel' is the wordplay.
I cannot quite understand how this works, but
'fuel' could be 'stoke' (I've seen this in another clue) and 'stoke' is located in the answer.
A single letter 'r' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for stoker that I've seen before include "turning to coke regularly to provide energy?" , "He's fuelled < the legend of Dracula" , "Vampires were subject to" , "One tending furnace" , "one adding fuel to the fire?" .)