Bluish-white metallic element (4)
I believe the answer is:
zinc
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bluish-white metallic element</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 zinc that I've seen before include "Metal much used in alloys" , "trace element" , "Type of metal" , "coat for protection" , "White metallic element used in alloys" .)