To rot (6)
I believe the answer is:
perish
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">to rot</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for perish that I've seen before include "Go off" , "Expire" , "Rot or suffer untimely death" , "fall" , "Die; decay" .)