Type of metal (4)
I believe the answer is:
zinc
'type of metal' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for zinc that I've seen before include "White metallic element used in alloys" , "It is used to coat iron against corrosion" , "Bluish-white metal" , "Metal used in brass" , "Metal used for galvanising steel" .)