Study before class how to fit in (7)
I believe the answer is:
conform
'to fit in' is the definition.
(thesaurus)
'study before class' is the wordplay.
'study' becomes 'con' (I've seen this before).
'before' means one lot of letters go next to another.
'class' becomes 'form' (form class is a kind of class**).
'con'+'form'='CONFORM'
'how' acts as a link.
(Other definitions for conform that I've seen before include "Comply with accepted rules" , "become fitter?" , "Fall into line" , "Keep to rules or general custom" , "Match" .)