Class put together (4)
I believe the answer is:
form
I believe this clue is a double definition.
'class' is the first definition.
(form class is a kind of class)
'put together' is the second definition.
(I've seen this in another clue)
(Other definitions for form that I've seen before include "Class; schedule" , "Part of school" , "Printed document with blank spaces for information to be inserted" , "Hare's home - something to be filled in" , "accommodation for hare" .)