Command rests with those on duty (9)
I believe the answer is:
orderlies
'those on duty' is the definition.
I can't judge whether this defines the answer.
'command rests' is the wordplay.
'command' becomes 'order' (order is a kind of command).
'rests' becomes 'lies' ('lie' can be a synonym of 'rest').
'order'+'lies'='ORDERLIES'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for orderlies that I've seen before include "Hospital workers" , "Hospital attendants or soldiers working for officers" , "Soldiers attending superior officers" , "Servants" , "Military or hospital attendants" .)