A in physics (6)
I believe the answer is:
ampere
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a in physics</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 ampere that I've seen before include "Current measure" , "Unit measured by 17 across" , "scientist" , "Solenoid inventor" , "Unit of currency" .)