The discipline of a fraternity (5)
I believe the answer is:
order
This clue is a double definition.
'the discipline' is the first definition.
(I've seen this before)
'a fraternity' is the second definition.
(I've seen this before)
'of' is the link.
(Other definitions for order that I've seen before include "Regular or proper arrangement" , "in which things are properly arranged?" , "Tidy state - that's a command" , "Edict, command" , "peace" .)