Influential expert (4)
I believe the answer is:
guru
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">influential expert</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 guru that I've seen before include "Hindu or Sikh religious teacher or leader" , "Wise leader" , "Swami" , "Name given to the each of the first ten leaders of the Sikh religion" , "Hindu or Buddhist spiritual teacher" .)