Gambling game permitted in the course of a journey (8)
I believe the answer is:
roulette
'gambling game' is the definition.
(roulette is a kind of gambling game)
'permitted in the course of a journey' is the wordplay.
'permitted' becomes 'let' (I've seen this before).
'in the course of' is an insertion indicator.
'a journey' becomes 'route' (I've seen this in other clues).
'let' inserted within 'route' is 'ROULETTE'.
(Other definitions for roulette that I've seen before include "sort of gambling" , "it's for the better, supposedly" , "Form of gambling" , "French gambling" , "Gambling game with spinning wheel and ball" .)