Floating marker (4)
I believe the answer is:
buoy
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">floating marker</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 buoy that I've seen before include "To raise" , "Anchored (navigation) float" , "Floating sea marker" , "Floating item often marking a hazard" , "Hearten" .)