Admission to the course (6)
I believe the answer is:
This clue is a double definition.
'admission' is the first definition.
(I know that admission can be written as entree)
'the course' is the second definition.
(course of a meal)
'to' acts as a link.
(Other definitions for entree that I've seen before include "Dish served between fish and meat courses" , "Dish conferring right of access" , "Served after the fish and before the main course" , "No way-out" , "Principal dish and right to enter" .)