The most common and most likely answer to this crossword clue is the 5 letter word TARES
T
A
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S
Buddy explains!

The straight part
We know that "Weeds" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case weeds = tares.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TARES mean?
TARES noun- A vetch, or the seed of a vetch (genus Vicia, esp. Vicia sativa)
- Any of the tufted grasses of genus Lolium; darnel.
- A damaging weed growing in fields of grain.
- The empty weight of a container; the tare weight or unladen weight.
- To take into account the weight of the container, wrapping etc. in weighting merchandise.
- To set a zero value on an instrument (usually a balance) that discounts the starting point.