Product of mine, light and strong — the second one's superfluous for Americans (9)
I believe the answer is:
aluminium
'product of mine light' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'and strong the second one's superfluous for americans' is the wordplay.
I cannot quite understand how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is found within the answer.
'second' could be 'ii' (Roman numerals, eg Charles II) and 'ii' is present in the remaining letters.
'one' could be 'a' (a thing is one thing) and 'a' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for aluminium that I've seen before include "Light metal" , "Al" , "Silvery metallic element" , "Lightweight metal" , "Metallic element found in bauxite" .)