Unit of magnetic flux density (5)
I believe the answer is:
tesla
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unit of magnetic flux density</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 tesla that I've seen before include "Inventive sort" , "Unit of magnetic flux density" , "Nikola ---, electricity pioneer" , "Californian company specialising in electric cars" , "SI unit; steal (anag.)" .)