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