Arrangement by command (5)
I believe the answer is:
order
This clue is a double definition.
'arrangement' is the first definition.
(order is a kind of arrangement)
'command' is the second definition.
(order is a kind of command)
'by' acts as a link.
(Other definitions for order that I've seen before include "Command, mandate" , "Symmetry" , "American helping" , "Direct - class - instruction" , "Family - group - arrangement" .)