"Stainless" metal (5)
I believe the answer is:
steel
'stainless metal' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for steel that I've seen before include "Form of iron" , "Structural metal alloy" , "Mixture of carbon and iron" , "Iron/carbon alloy" , "The staying power" .)