Blacksmiths' blocks (6)
I believe the answer is:
anvils
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">blacksmiths' blocks</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for anvils that I've seen before include "Heavy blocks for the blacksmith" , "Blocks for a blacksmith to work on" , "Heavy blocks for blacksmiths" , "Iron blocks for blacksmiths" , "Iron blocks for hammering hot metal" .)