Galvanizing metal (4)
I believe the answer is:
zinc
'galvanizing metal' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for zinc that I've seen before include "Mineral" , "Penultimate element (alpha. order)" , "Metallic element present with copper in brass" , "Constituent of brass" , "it might be galvanising" .)