A pass back may be just the ticket (6)
I believe the answer is:
return
'ticket' is the definition.
(return ticket is a kind of ticket)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for return that I've seen before include "Retort" , "answer" , "election to parliament" , "Comeback" , "Send/come back" .)