Biblical weed (4)
I believe the answer is:
tare
'biblical weed' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tare that I've seen before include "Vessel's weight" , "Common vetch" , "Variety of vetch" , "Allowance made for the weight of the container in which goods are packed" , "Vetch plant" .)