Metal deposit (4)
I believe the answer is:
lode
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">metal deposit</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 lode that I've seen before include "Deposit of valuable ore found in surrounding rocks" , "Deposit of valuable ore running through other rocks" , "Rich source" , "Vein of metal ore in surrounding rocks" , "Vein of metal in the earth" .)