Electromotive force (7)
I believe the answer is:
voltage
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">electromotive force</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for voltage that I've seen before include "current potential" , "Measure of electrical potential" , "Power supply rating" .)