They make very fine traps (7)
I believe the answer is:
spiders
This might be a double definition.
'they' is the first definition.
Both the answer and definition are plural nouns.
Perhaps there's an association between them I don't understand?
'very fine traps' is the second definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'make' is the link.
Can you help me to learn more?
(Other definitions for spiders that I've seen before include "Insects; rests" , "Predators on the web" , "Web weavers" , "Arachnids" , "14 [BOWIE] 's band from 26 [MARS]" .)