A union group (4)
I believe the answer is:
knot
This clue could be a double definition.
'a union' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'group' is the second definition.
The answer is an example.
Can you help me to learn more?
(Other definitions for knot that I've seen before include "Tie (or what one puts in it?)" , "binder?" , "Something tied" , "Measure of speed of, for example, frigate" , "puzzle" .)