Someone who has one too many after wedding (8)
I believe the answer is:
bigamist
'someone who has one too many after wedding' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's a link between them I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for bigamist that I've seen before include "Person who commits crime of marrying while still married to another" , "One married to two people at once" , "Man with two wives" , "Law-breaker with more than one spouse" , "lawbreaking union member" .)