A commodity extensively used (7)
I believe the answer is:
elastic
'a commodity' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for elastic that I've seen before include "Like some bands" , "Kind of band" , "Scale it (anag.)" , "Tape containing flexible rubber" , "Able to give a bit" .)