Prone, apt (to) (6)
I believe the answer is:
likely
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">prone</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">apt to</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ ></span>
(Other definitions for likely that I've seen before include "On the cards" , "In prospect" , "In all probability" , "Probable, expected" , "Promising; probable" .)