Shortcoming, flaw (8)
I believe the answer is:
weakness
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">shortcoming</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">flaw</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for weakness that I've seen before include "Infirmity" , "Flaw, failing" , "Frailty - flaw" , "Achilles heel" , "Ill-defended spot - predilection" .)