Shakespeare's fairy king (6)
I believe the answer is:
oberon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">shakespeare's fairy king</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for oberon that I've seen before include "King of the fairies, husband of Titania" , "Satellite" , "Borneo (anag)" , "King of the fairies (AMND)" , "MND fairy king" .)