Ruin; annihilate (7)
I believe the answer is:
destroy
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">ruin</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">annihilate</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for destroy that I've seen before include "put to death" , "Soundly defeat" , "'Demolish, ruin (7)'" , "Get rid of" , "Kill; ruin" .)