Post office workers (5)
I believe the answer is:
staff
This clue is a double definition.
'post' is the first definition.
(I've seen this before)
'office workers' is the second definition.
(I've seen this in another clue)
(Other definitions for staff that I've seen before include "Rules needed for scoring" , "Employees; rod" , "Baton" , "Stick of authority" , "Hands" .)