Two classes make up a forme (7)
I believe the answer is:
typeset
'make up a forme' is the definition.
(a forme is a body of type in printing)
'two classes' is the wordplay.
'two classes' means two replacements for 'class'.
'class' becomes 'type' (both can mean a variety or kind).
'class' becomes 'set' (I've seen this in other clues).
'type'+'set'='TYPESET'
(Other definitions for typeset that I've seen before include "Ready to be printed" , "Arrange (text) for printing" , "Ready to go public" , "Prepare (text) for printing" , "Like" .)