Large shell (5)
I believe the answer is:
conch
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">large shell</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 conch that I've seen before include "Large shell used as trumpet" , "Big spiral-shelled mollusc" , "Big spiral shell" , "Type of shell" , "Large spiral shell" .)