Lowest deck (5)
I believe the answer is:
orlop
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lowest deck</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 orlop that I've seen before include "deck at the lowest point" , "Lowest deck of a wooden sailing ship" , "Ship's lowest deck" , "part of ship" , "hold covering" .)