Firth of Clyde island (5)
I believe the answer is:
arran
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">firth of clyde 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 arran that I've seen before include "Scottish territory" , "Scottish island" , "Isle near Firth of Clyde" , "Firth of Clyde island" .)