Fashionable fraternity properly arranged (2,5)
I believe the answer is:
in order
'properly arranged' is the definition.
(I've seen this before)
'fashionable fraternity' is the wordplay.
'fashionable' becomes 'in' ('in' can be similar in meaning to 'fashionable').
'fraternity' becomes 'order' (I've seen this before).
'in'+'order'='IN ORDER'
(Other definitions for in order that I've seen before include "fitting" , "Able to operate" , "Settled" , "as many nuns are" , "Nun may be" .)