Seaside structure (4)
I believe the answer is:
pier
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">seaside structure</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for pier that I've seen before include "sight at the seaside" , "'Dock, wharf (4)'" , "Mole, wall between windows" , "Breakwater; arch pillar" , "Wharf jutting out into water" .)