The most common and most likely answer to this crossword clue is the 6 letter word PEYOTE
P
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More clues leading to the result PEYOTE
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 = peyote.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 PEYOTE mean?
PEYOTE noun- A small, spineless cactus (Lophophora williamsii) found from southwest United States to central Mexico that produces buttonlike tubercles that can be chewed for its psychedelic effect, primarily from the drug mescaline.
- A mescal button produced by the plant.