Class discipline (5)
I believe the answer is:
order
I believe this is a double definition.
'class' is the first definition.
(I've seen this in another clue)
'discipline' is the second definition.
(I've seen this before)
(Other definitions for order that I've seen before include "Enjoin in harmony" , "American helping" , "Command harmony" , "Decree" , "Uniformity or fraternity" .)