。
Don't look down on your subordinates.
Literal
Subordinates [obj-を] neglect [prohibition-な].
目下の者 ('those below one' = subordinates) uses 目下 (めした) in its hierarchical sense — distinct from もっか ('currently'). ないがしろにする ('treat with contempt, neglect') is a somewhat literary expression. ~するな is the blunt prohibitive — dictionary form + な.