Act in accordance with class (7)
I believe the answer is:
perform
'act' is the definition.
(eg to perform or act on stage)
'in accordance with class' is the wordplay.
'in accordance with' becomes 'per' (I've seen this in another clue).
'class' becomes 'form' (synonyms).
'per'+'form'='PERFORM'
(Other definitions for perform that I've seen before include "Carry out; act" , "Carry out, accomplish" , "Act - accomplish" , "Act or execute" , "Carry out (duties)" .)