Yaw (4)
I believe the answer is:
veer
'yaw' is the definition.
(I know that yaw is a more specific form of the action the veer)
This is all the clue.
(Other definitions for veer that I've seen before include "Deviate" , "Change direction sharply" , "Swing around" , "Swerve" , "Suddenly change direction" .)