Gambling game permitted in a way (8)
I believe the answer is:
roulette
'gambling game' is the definition.
(roulette is a kind of gambling game)
'permitted in a way' is the wordplay.
'permitted' becomes 'let' (I've seen this before).
'in' means one lot of letters goes inside another.
'a way' becomes 'route' (route is a kind of way).
'let' put within 'route' is 'ROULETTE'.
(Other definitions for roulette that I've seen before include "Gambling activity" , "risky venture" , "Gambling game with spinning wheel and ball" , "Gambling device" , "Half of 1D [GAME OR BIRD]" .)