The most common and most likely answer to this crossword clue is the 8 letter word NEPENTHE
I've seen this crossword clue in Financial Times
N
E
P
E
N
T
H
E
More clues leading to the result NEPENTHE
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 = nepenthe.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 NEPENTHE mean?
NEPENTHE noun- A drug mentioned in Homer's Odyssey (c. 8th century B.C.E.) as bringing relief from anxiety or grief; hence, any drug or substance seen as bringing welcome forgetfulness or relief.
- A Southeast Asian carnivorous plant of the genus Nepenthes; a monkey cup or tropical pitcher plant.