Tidal retreat (3)
I believe the answer is:
ebb
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tidal retreat</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 ebb that I've seen before include "Receding movement, as of a tide" , "(Sea) recede" , "Initially Mrs Browning's" , "recession" , "Tidal retreat" .)