Course followed without permit for gambling activity (8)
I believe the answer is:
roulette
'gambling activity' is the definition.
(I've seen this before)
'course followed without permit' is the wordplay.
'course followed' becomes 'route' (I've seen this before).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'permit' becomes 'let' ('let' can be a synonym of 'permit').
'route' going around 'let' is 'ROULETTE'.
'for' is the link.
(Other definitions for roulette that I've seen before include "Gambling game with spinning wheel and ball" , "Wheel of fortune" , "If Russian, it's a very dangerous game" , "Casino game" , "Wheel for the gambler" .)