Pupils of the past perhaps (6)
I believe the answer is:
alumni
'pupils' is the definition.
(I have seen 'Former pupils' mean 'alumni' so perhaps 'pupils' could also mean 'alumni')
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for alumni that I've seen before include "Old boys and girls" , "Former (college) students" , "Graduates of an institution" , "Past pupils, former students" , "we studied at a certain place" .)