Ebbing and flowing (5)
I believe the answer is:
tidal
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ebbing and flowing</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tidal that I've seen before include "Subject to ebb and flow" , "Concerning the rise and fall of the sea" , "Concerning lunar-driven ocean movements" , "To do with movement of seas" , "Subject to moon's pull" .)