Test ore (5)
I believe the answer is:
assay
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">test ore</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 assay that I've seen before include "Test ore for content" , "Put to the proof" , "Test of substance" , "Test, or say, to establish quality" , "Analyse ore for metal content" .)