Obstructed service during journey? You can bet on it (8)
I believe the answer is:
roulette
'you can bet on it' is the definition.
(gambling game)
'obstructed service during journey?' is the wordplay.
'obstructed service' becomes 'let' (tennis term).
'during' is an insertion indicator.
'journey?' becomes 'route' (I've seen this in other clues).
'let' going inside 'route' is 'ROULETTE'.
(Other definitions for roulette that I've seen before include "Casino game" , "it's a gamble" , "Gambling game with small ball and revolving disc (8)" , "Half of 1D [GAME OR BIRD]" , "Spinning-wheel game" .)