Set off stuck in reverse, disheartened (6)
I believe the answer is:
depart
'set off' is the definition.
(synonyms)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for depart that I've seen before include "Make an exit" , "Take one's leave, go" , "Go away; deviate" , "make tracks" , "Stray" .)