Petrol, for example (4)
I believe the answer is:
fuel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">petrol for example</span>' is the definition.<br/ ><span class="explanation-format__explanation">(petrol is a kind of fuel)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for fuel that I've seen before include "Material for burning" , "Power source; inflame" , "coal etc" , "Combustible material" , "Material fed to flames" .)