Lesson resorting to ritual (8)
I believe the answer is:
tutorial
'lesson' is the definition.
(I've seen this before)
'resorting to ritual' is the wordplay.
'resorting' indicates an anagram.
'to'+'ritual'='toritual'
'toritual' is an anagram of 'TUTORIAL'.
(Other definitions for tutorial that I've seen before include "Study meeting" , "Period of individual instruction" , "Teaching session for a small number of students" , "Conference" , "Session with a private instructor" .)