Should a vegetable grower know his well? (6)
I believe the answer is:
onions
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for onions that I've seen before include "Tearful bulbs" , "Pungent bulbs (6)." , "Punguent bulbs" , "Knowing these vegetables, you'd be well up" , "If you knew your vegetables, you'd be well up" .)