Vetch plant (4)
I believe the answer is:
tare
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vetch plant</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tare that I've seen before include "Biblical weed" , "Allowance made for the weight of the container in which goods are packed" , "Allowance for package weight; vetch" , "Weedy annual grass, often occurs in grainfields" , "Vehicle's empty weight" .)