Everglades deposit (4)
I believe the answer is:
peat
'everglades deposit' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for peat that I've seen before include "Fuel dug from bog" , "Tape (anag.)" , "Partially carbonised vegetable matter used as a fuel when dried" , "Form of fuel" , "Decomposed vegetable matter" .)