Trick to get class to fall in line (7)
I believe the answer is:
conform
'fall in line' is the definition.
(I've seen this before)
'trick to get class' is the wordplay.
'trick' becomes 'con' (I've seen this before).
'to get' is a charade indicator (letters next to each other).
'class' becomes 'form' (form class is a kind of class**).
'con'+'form'='CONFORM'
'to' acts as a link.
(Other definitions for conform that I've seen before include "Follow the crowd" , "Run with the pack" , "Toe the line" , "Adapt" , "Follow the herd" .)