Tin alloy (6)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tin alloy</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for pewter that I've seen before include "An alloy of tin with a small amount of other metal" , "Grey alloy of tin and lead, makes mugs etc." , "Alloy of tin and lead, often in beer mug" , "Tin alloy used to make plates and mugs" , "prize-money" .)