Alloy of tin and lead (6)
I believe the answer is:
pewter
'alloy of tin and lead' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for pewter that I've seen before include "Tin alloy for utensils" , "Grey alloy of tin and lead, often in mug" , "Tin alloy used to make plates and mugs" , "Grey alloy of tin and lead, makes mugs etc." , "Bluish-grey alloy" .)