Ability, proficiency (5)
I believe the answer is:
skill
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">ability</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(skill is a kind of ability)</span><br/ ><br/ >'<span class="explanation-format__original">proficiency</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for skill that I've seen before include "Special ability" , "facility" , "Aptitude" , "Ability - dexterity" , "Craft; dexterity" .)