A member of many unions (10)
I believe the answer is:
polygamist
This clue could be a double definition.
'a member' is the first 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?
'of many unions' is the second definition.
The definition suggests a singular noun which matches the answer.
Can you help me to learn more?
(Other definitions for polygamist that I've seen before include "Great family man" , "not being single-minded" , "One multiply-spliced" , "One with multiple spouses" , "Person multiply married" .)