Twisting force (6)
I believe the answer is:
torque
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">twisting force</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 torque that I've seen before include "Source of spin" , "Force that produces rotation" , "Metal necklace; also a measure of force" , "Force causing rotation in mechanism" , "measure of twist" .)