A metallic element (6)
I believe the answer is:
metals
'a metallic element' is the definition.
(I know that metallic element can be written as metals)
This is the entire clue.
(Other definitions for metals that I've seen before include "Gold and silver, say" , "Copper, tin and iron" , "Silver and aluminium, say" , "Silver and platinum, say" , "Such as iron, gold, etc" .)