Siren's sound (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">siren's sound</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 wail that I've seen before include "blub" , "Utter a long sad cry" , "Cry of lament" , "Cry of grief" , "Long cry, as of siren" .)