Leave the track (6)
I believe the answer is:
derail
'leave the track' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for derail that I've seen before include "Cause to leave the tracks" , "Cause to run off the tracks" , "come off the line" , "Force off track, like a train" , "create an obstructive diversion" .)