Organic fuel (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">organic fuel</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for peat that I've seen before include "Bog vegetable matter, turf" , "Vegetable deposit used as fuel and fertiliser" , "Fuel dug from bog" , "Natural solid fuel" , "Dried turf" .)