A snake round someone's neck! (3)
I believe the answer is:
boa
This clue might be a double definition.
'a snake' is the first definition.
(I know that boa is a type of constrictor)
'round someone's neck' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
Can you help me to learn more?
(Other definitions for boa that I've seen before include "Snake; feather stole" , "Potential killer" , "Wrap" , "One with scaly body" , "Python" .)