Impart knowledge during class (6)
I believe the answer is:
inform
'impart knowledge' is the definition.
(I've seen this before)
'during class' is the wordplay.
'during' becomes 'in' (e.g. during February means in February).
'class' becomes 'form' (form class is a kind of class).
'in'+'form'='INFORM'
(Other definitions for inform that I've seen before include "effective" , "Give information to (someone)" , "Impart knowledge" , "Tell - shop" , "Give knowledge to" .)