Copper and zinc, for instance, used in the foundation? (4,6)
I believe the answer is:
base metals
'instance used in the foundation?' is the definition.
I know nothing about this answer so I can't judge whether this works.
'copper and zinc' is the wordplay.
'copper' becomes 'base metal' (I've seen this before).
'and' means one lot of letters go next to another.
'zinc' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'basemetal'+'s'='BASE METALS'
'for' is the link.
Can you help me to learn more?
(Another definition for base metals that I've seen is " Lead with others in group".)