Bang (4)
(Other definitions for thud that I've seen before include "Dull heavy noise" , "Dull, heavy sound" , "Sound of a heavy fall" , "Sound made by impact of heavy objects" , "Dull bang" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bang</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that bang can be written as slam)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for slam that I've seen before include "Hit hard" , "ambitious bid" , "Taking of twelve or thirteen tricks (bridge)" , "Severely criticise; shut (a door) forcefully" , "major contract" .)