Profit on a ticket? (6)
I believe the answer is:
return
I believe this clue is a double definition.
'profit' is the first definition.
(I've seen this before)
'a ticket?' is the second definition.
(return ticket is a kind of ticket)
'on' acts as a link.
(Other definitions for return that I've seen before include "Proceeds" , "Profit earned on money" , "Retort" , "Two-way ticket" , "Reappear" .)