Force tending to cause rotation (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
torque
(Other definitions for torque that I've seen before include "Rotational force; roquet (anag.)" , "Mechanical force causing rotation" , "Turning force" , "Twisted metalwork" , "Metal necklace; also a measure of force" .)