Saint carrying tungsten alloy (6)
I believe the answer is:
pewter
'alloy' is the definition.
(I know that pewter is a type of alloy)
'saint carrying tungsten' is the wordplay.
'saint' becomes 'peter' (I've seen this before).
'carrying' indicates putting letters inside.
'tungsten' becomes 'W' (W is the chemical symbol for tungsten).
'peter' going around 'w' is 'PEWTER'.
(Other definitions for pewter that I've seen before include "Alloy of tin with copper and antimony" , "Tin alloy for utensils" , "Grey alloy used for making mugs" , "An alloy of tin with a small amount of other metal" , "Beer-tankard alloy" .)