Heavy weight (3)
I believe the answer is:
ton
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">heavy weight</span>' is the definition.<br/ ><span class="explanation-format__explanation">(a ton weighs a lot)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for ton that I've seen before include "Two thousand, two hundred and forty lb" , "Heavy weight or 100mph" , "1000 kilos" , "20 cwt" , "High-speed" .)