Straying from the right course (6)
I believe the answer is:
errant
'straying from the right course' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for errant that I've seen before include "Off the mark, wandering" , "looking for adventure" , "Root vegetable" , "Straying from the right course" , "Straying; knight" .)