The most common and most likely answer to this crossword clue is the 10 letter word BELLADONNA
I've seen this crossword clue in The Daily Telegraph
B
E
L
L
A
D
O
N
N
A
More clues leading to the result BELLADONNA
- Siren trouble girl raised as blooming deadly thing?
- Two women together are poison
- Drug two Italian girls?
- Rebel lad on Nauru smuggling drug
- Drug brought about everything in break-up of one band
- Call a fellow about new advanced drug
- Boy in Lebanon destroyed poisonous plant
- Call girl hosting party, a poisonous thing
- Poison boy consumed in Lebanon, sadly
- Ring a teacher at university over North American drug
Buddy explains!

The straight part
We know that "drug" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case drug = belladonna.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 BELLADONNA mean?
BELLADONNA noun- A plant, Atropa belladonna, having purple bell-shaped flowers and poisonous black glossy berries.
- An alkaloid extracted from this plant, sometimes used medicinally, containing atropine.