Lesson or lecture (5)
I believe the answer is:
class
I believe this clue is a double definition.
'lesson' is the first definition.
(synonyms)
'lecture' is the second definition.
(academic class)
(Other definitions for class that I've seen before include "High-quality" , "Set, category" , "Genus" , "Body of students" , "26 [ORDER]" .)