Posted popular class edition (8)
I believe the answer is:
informed
'posted' is the definition.
(thesaurus)
'popular class edition' is the wordplay.
'popular' becomes 'in'.
'class' becomes 'form' (form class is a kind of class).
'edition' becomes 'ed'.
'in'+'form'+'ed'='INFORMED'
(Other definitions for informed that I've seen before include "Gave knowledge to" , "Knowledgeable or briefed" , "Imparted knowledge" , "Expert" , "Told" .)