Does he govern where to draw the line? (5)

I believe the answer is:
ruler
'does he govern where' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'draw the line?' is the wordplay.
'draw' becomes 'rule' (ruling is a kind of drawing).
'the line?' becomes 'r' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rule'+'r'='RULER'
'to' is the link.
Can you help me to learn more?
(Other definitions for ruler that I've seen before include "Queen maybe" , "Measuring strip" , "Despot perhaps" , "overlord" , "that should go straight" .)
