Sovereign for stationery item (5)
I believe the answer is:
ruler
I believe this is a double definition.
'sovereign' is the first definition.
(I've seen this before)
'stationery item' is the second definition.
(I've seen this before)
'for' acts as a link.
(Other definitions for ruler that I've seen before include "It can be used to strike" , "that should go straight" , "Stationery item" , "Strip used in drawing straight lines" , "' - - of the Queen's Navee!'" .)