Drawing aid from head of state (5)
I believe the answer is:
ruler
This clue is a double definition.
'drawing aid' is the first definition.
(I've seen this before)
'head of state' is the second definition.
(I've seen this before)
'from' acts as a link.
(Other definitions for ruler that I've seen before include "Maharaja, e.g." , "measure applied in school?" , "Stationery item" , "Straight edge for drawing lines" , "One for drawing lines" .)