Proficiently (4)
I believe the answer is:
well
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">proficiently</span>' is the definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for well that I've seen before include "Issue forth" , "Flow up" , "Bore; very much" , "Lift-shaft" , "Source; in good health" .)