Stumble on journey (4)
I believe the answer is:
trip
I believe this is a double definition.
'stumble' is the first definition.
(I know that stumble can be written as trip)
'journey' is the second definition.
(I know that journey is a kind of the trip)
'on' is the link.
(Other definitions for trip that I've seen before include "Ride" , "Hallucinatory experience" , "day out?" , "In close confrontation" , "Accidental misstep" .)