Belfast's county (6)
I believe the answer is:
antrim
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">belfast's county</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for antrim that I've seen before include "County of northeast Ireland" , "town in Ireland" , "Irish county of musically green glens" , "N Ireland county of green glens" , "Giant's Causeway county" .)