Harmful, toxic (7)
I believe the answer is:
noxious
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">harmful</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(associated in meaning)</span><br/ ><br/ >'<span class="explanation-format__original">toxic</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(associated in meaning)</span><br/ ><br/ ></span>
(Other definitions for noxious that I've seen before include "Unpleasant and harmful" , "Harmful, poisonous" , "Harmful to health" , "Pernicious" , "Harmful, toxic" .)