Big dud (4)
I believe the answer is:
flop
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">big dud</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 flop that I've seen before include "Complete failure" , "Dud - bomb" , "Failure - loll" , "crash" , "turkey" .)