The most common and most likely answer to this crossword clue is the 6 letter word PROZAC
I've seen this crossword clue in Independent
P
R
O
Z
A
C
More clues leading to the result PROZAC
- Happy pill for Mr Efron?
- Something to dispel gloom like some Richmond voters formerly?
- Drug for case of zoophobia, heading for cage
- Antidepressant for unsuccessful London mayoral election candidate
- The last letter in copra possibly gives you an anti-depressant
- Drug for unknown aches he’s left
- Prescribed drug, complain about gaining weight
- The last character cutting copra concocted something for depression
- Retired nag carrying weight needs medication
- In favour of person ennobled by Boris providing 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 = prozac.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.