Weedkiller (9)
I believe the answer is:
herbicide
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">weedkiller</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 herbicide that I've seen before include "Chemical agent that destroys plants" , "Substance toxic to plants" , "Weedkiller" , "Vegetation destroyer" , "Plant killer" .)