Iron or gold for instance (5)
I believe the answer is:
metal
This clue is a double definition.
'iron' is the first definition.
(I've seen this before)
'gold for instance' is the second definition.
(I've seen this in another clue)
(Other definitions for metal that I've seen before include "lead as one" , "Solid material, a good conductor of heat and electricity" , "employed in making roads" , "Alloy" , "Given lead, perhaps" .)