Special skill (9)
(Other definitions for expertise that I've seen before include "Special skill or knowledge" , "Craft" , "professionalism" , "Technical skill" , "Mastery, proficiency" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">special skill</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for knack that I've seen before include "Skill in doing something" , "Slope" , "Ability, facility" , "Technical aptitude" , "Skill for specific task" .)