King married old woman (5)
I believe the answer is:
crone
'old woman' is the definition.
(crone is a kind of old woman)
'king married' is the wordplay.
'king' becomes 'cr' (short for Carolus Rex, King Charles in Latin).
'married' becomes 'one' (I've seen this in another clue).
'cr'+'one'='CRONE'
(Other definitions for crone that I've seen before include "withered old woman" , "old-womanish type" , "Witch" , "Ugly old woman" , "Old hag" .)