Lead ore (6)
I believe the answer is:
galena
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lead ore</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for galena that I've seen before include "Len, GAA produces lead sulphide" , "Commonest ore of lead - Angle "A" (anag)" , "Angela (anag) - ore producing lead" , "Lead sulphide mineral" .)