Law right for sovereign (5)
I believe the answer is:
ruler
'for sovereign' is the definition.
(I've seen this in another clue)
'law right' is the wordplay.
'law' becomes 'rule' (rule is a kind of law).
'right' becomes 'r' (abbreviation).
'rule'+'r'='RULER'
(Other definitions for ruler that I've seen before include "Emperor, maybe" , "Straight edge; monarch" , "Commander" , "Straight edge for drawing lines" , "Sovereign - support for a firm line!" .)