A Balearic island (5)
I believe the answer is:
ibiza
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">a balearic island</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 ibiza that I've seen before include "part of Spain" , "resort island" , "Spanish island" , "Clubbers' island" , "One of matching pair" .)