Gambling activity permitted in course (8)
I believe the answer is:
roulette
'gambling activity' is the definition.
(I've seen this before)
'permitted in course' is the wordplay.
'permitted' becomes 'let' (I've seen this before).
'in' means one lot of letters goes inside another.
'course' becomes 'route' (I've seen this before**).
'let' put into 'route' is 'ROULETTE'.
(Other definitions for roulette that I've seen before include "If Russian, it's a very dangerous game" , "SPORT/GAME" , "Game of chance with small ball" , "Wheel of fortune" , "Spinning-wheel game" .)