Ingredient of concrete (6)
I believe the answer is:
cement
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ingredient of concrete</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for cement that I've seen before include "Stick together - substance used by a builder" , "joiner" , "Glue" , "Powder substance to make concrete" , "Bind firmly" .)