Two classes prepared for printing (7)
I believe the answer is:
typeset
'prepared for printing' is the definition.
(I've seen this in another clue)
'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 "compositor" , "Prepare (text) for printing" , "(Of fonts) ready to print" , "characters lined up ready for a run-off?" , "Ready to go public" .)