Arrange by command (5)
I believe the answer is:
order
I believe this clue is a double definition.
'arrange' is the first definition.
(I know that arrange can be written as order)
'command' is the second definition.
(I know that order is a type of command)
'by' acts as a link.
(Other definitions for order that I've seen before include "One may be tall if demanding" , "Rank" , "One of Great Lakes" , "Direction; class; arrange" , "architectural style" .)