Complete journey on bullet train? (5,4)
I believe the answer is:
round trip
'complete journey' is the definition.
(term for the entirety of a journey)
'on bullet train?' is the wordplay.
'on' says to put letters next to each other.
'bullet' becomes 'round'.
'train?' becomes 'trip' (I can't justify this - if you can you should give a lot more credence to this answer).
'round' next to 'trip' is 'ROUND-TRIP'.
(Other definitions for round trip that I've seen before include "ending where you started - with 14a" , "Journey that gets you back home" , "bar and back?" , "kind of voyage" , "whole journey" .)