Bog fuel (4)
I believe the answer is:
peat
'bog fuel' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for peat that I've seen before include "Fuel dug from bog" , "Some got energy from this" , "load of stuff in the garden?" , "Partially carbonised vegetable matter used as a fuel when dried" , "Dried turf" .)