Levels of command (8)
I believe the answer is:
echelons
'levels of command' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for echelons that I've seen before include "Len chose levels or grades" , "Levels of rank, could be upper" , "Levels of authority" , "Levels or ranks in an organization" .)