It's only natural that one should form an attachment (3)
I believe the answer is:
bur
'attachment' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe there's a link between them I don't understand?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for bur that I've seen before include "Prickly seed case" , "Clinging seed case" , "small drill" , "sticker" , "Seed-case" .)