Origin, it's said, in regular journey (5)
I believe the answer is:
route
'regular journey' is the definition.
(I've seen this before)
'origin it's said' is the wordplay.
'origin' becomes 'root' ('root' can be a synonym of 'origin').
'it's said' indicates a 'sounds like' (homophone) clue.
'root' is a homophone of 'ROUTE'.
'in' is the link.
(Other definitions for route that I've seen before include "Way, course" , "The way to get somewhere" , "Path taken" , "Way, line" , "Course to destination" .)