Veer off course (3)
I believe the answer is:
yaw
'veer off course' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for yaw that I've seen before include "Temporarily get off course" , "Go off course" , "(Of ship) twist sideways" , "Deviation (of e.g. ship)" , "Deviate off course" .)