Mooring device (6)
I believe the answer is:
anchor
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mooring device</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 anchor that I've seen before include "No arch when you drop it, oddly" , "Stabilise" , "Be moored" , "Brake for a boat" , "A weight to secure in place" .)