Half-moon tide (4)
I believe the answer is:
neap
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">half-moon tide</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 neap that I've seen before include "Small tide" , "A less than average tide" , "Tide with least fall and rise of water" , "Sort of tide" , "It's between spring and ebb" .)