1000 kilograms (5)
I believe the answer is:
tonne
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">1000 kilograms</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 tonne that I've seen before include "Metric weight unit" , "One thousand kilograms" , "Mass" , "1000 kilograms" , "1,000 kg" .)