Staff note (4)
I believe the answer is:
memo
'staff note' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for memo that I've seen before include "Written business message, in short" , "Note written as a reminder" , "A little something to be remembered" , "- Currie, Br. politician" , "Brief note, usually between co-workers" .)