Heads off (6)
I believe the answer is:
averts
'heads off' is the definition.
('avert' can be a synonym of 'head off')
This is all the clue.
(Other definitions for averts that I've seen before include "Stops" , "Turns aside" , "Deflects, heads off" , "Of eyes or gaze, turns away" , "Wards off" .)