Jed Clampett's discovery
I believe the answer is:
oil
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">jed clampett's discovery</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for oil that I've seen before include "Fluid lubricant" , "Liquid fuel" , "valuable commodity" , "Lubricate; fuel" , "Lubricant or petroleum" .)