Part of pewter (3)
I believe the answer is:
tin
'part of pewter' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tin that I've seen before include "With copper, makes bronze" , "Silvery metallic element" , "Silvery-white metal used in cans" , "Metal element" , "Silvery white metal" .)