Remain in staff (5)
I believe the answer is:
stick
This clue is a double definition.
'remain' is the first definition.
(thesaurus)
'staff' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for stick that I've seen before include "Adhere; baton" , "Adhere - cane" , "Switch < put up" , "Baton; gum" , "Join firm" .)