Receding (6)
I believe the answer is:
ebbing
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">receding</span>' is the definition.<br/ ><span class="explanation-format__explanation">(ebbing is a kind of receding)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ebbing that I've seen before include "Gradually growing less" , "Flowing out" , "Big Ben (anag)" , "Receding like Big Ben" , "in decline?" .)