One who's twice hitched illegally (8)
I believe the answer is:
bigamist
'one who's twice hitched illegally' is the definition.
This is all the clue.
(Other definitions for bigamist that I've seen before include "lawbreaking union member" , "Law-breaker with more than one spouse" , "member of two unions" , "One marrying too often" , "Marital cheat" .)