Highly skilled (12)
(Other definitions for masterful that I've seen before include "Domineering" , "Dominant" , "overbearing" , "Having dominating quality" , "Authoritative" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">highly skilled</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for accomplished that I've seen before include "Talented - performed" , "Highly skilled" , "Highly proficient" , "executed" , "Performed - completed - with a high degree of skill" .)