Not so much to do in class (6)
I believe the answer is:
lesson
'class' is the definition.
(I know that class can be written as lesson)
'not so much to do in' is the wordplay.
'not so much' becomes 'less' (I've seen this before).
'to do in' becomes 'on' (I can't explain this - if you can you should believe this answer much more).
'less'+'on'='LESSON'
Can you help me to learn more?
(Other definitions for lesson that I've seen before include "Piece of instruction" , "A sermon or tutorial" , "Teaching unit" , "Unit of instruction" , "warning message" .)