Tankard material (6)
I believe the answer is:
pewter
'tankard material' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pewter that I've seen before include "Alloy of tin with copper and antimony" , "Alloy of tin and lead, often in beer mug" , "Tin alloy for utensils" , "Tin alloy used to make plates and mugs" , "Grey alloy used for making mugs" .)