Liable, prone (3)
I believe the answer is:
apt
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">liable</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">prone</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for apt that I've seen before include "Proper" , "Appropriate for Pat" , "Fit, suitable" , "Liable" , "Tending" .)