Weakness, vulnerable point (8,4)
I believe the answer is:
achilles heel
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">weakness</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">vulnerable point</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for achilles heel that I've seen before include "vulnerability" , "Personal weak spot" , "A chink in the armour" , "Person's vulnerable weakness" , "One's most vulnerable spot" .)