Grinding teeth (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">grinding teeth</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Another definition for molars that I've seen is " Grinding back teeth".)
(Other definitions for gnashing that I've seen before include "Grinding together, teeth perhaps" , "''There will be weeping and ... of teeth ...'' (Bible)" .)