Monarch (5)
'monarch' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ruler that I've seen before include "Monarch; measurer" , "Monarch or measure" , "Queen maybe" , "One measures" , "Leader - line-drawing aid" .)
'monarch' is the definition.
(female monarch)
This is all the clue.
(Other definitions for queen that I've seen before include "One in a suit" , "Female cat" , "Empress" , "powerful man on board" , "Playing card; bee" .)
'monarch' is the definition.
(male monarch)
This is all the clue.
(Other definitions for king that I've seen before include "and 21 Across: Shakespeare play" , "Playing card" , "VIP" , "Sovereign" , "Recipient of 10 21 [VELODROME GOLD]" .)
'monarch' is the definition.
(synonyms)
This is all the clue.
(Other definitions for sovereign that I've seen before include "Supreme ruler" , "Outstanding" , "Old gold coin" , "Ruler - gold coin" , "Monarch - old coin" .)
'monarch' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for potentate that I've seen before include "Mogul" , "A monarch or ruler" , "authority" , "Powerful autocratic ruler" .)
'monarch' is the definition.
(synonyms)
This is the entire clue.
(Another definition for crowned head that I've seen is " King or queen".)