Riverside embankment (5)
I believe the answer is:
levee
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">riverside embankment</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 levee that I've seen before include "Flood embankment" , "protection for bank" , "Early morning reception by a monarch" , "Gathering" , "Artificial embankment" .)