Seminar many miss (5)
I believe the answer is:
class
'seminar' is the definition.
(I've seen this before)
'many miss' is the wordplay.
'many' becomes 'c' (C is the Roman numeral for l00).
'miss' becomes 'lass' (lass is a kind of miss).
'c'+'lass'='CLASS'
(Other definitions for class that I've seen before include "Study group" , "It may appear after working" , "Group of students" , "Category; form" , "Standing" .)