Halloween cry (3)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">halloween cry</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 boo that I've seen before include "Catcall" , "Expression of disapproval" , "Sound expressing disapproval" , "Voice disapproval" , "Shout in disgust" .)
(Other definitions for trick or treat that I've seen before include "October 31 blackmail" , "Halloween custom" , "Children's protection racket at Hallowe'en?" , "Halloween ordeal?" , "Unwelcome Halloween tradition" .)