The most common and most likely answer to this crossword clue is the 10 letter word APOTHECARY
I've seen this crossword clue in Independent
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More clues leading to the result APOTHECARY
- A drug man, roughly, with tips for remedy?
- About to be involved in a commotion over variable old pharmacist
- Chemist needing a drug — he runs out of stock
- Old drug dealer a hearty cop busted
- Cry for attention outside Vauxhall, perhaps, by a cannabis dealer, old-style
- Try a cheap high, with nothing in it for drug supplier
- A cheap Tory involved with drugdealer
- A drug dealer’s yacht, and a rope thrown out
- Drug dealer has 3 drugs in a car at the end of driveway
- Pay actor questionably sheltering male drug dealer?
Buddy explains!

The straight part
We know that "Old drug dealer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old drug dealer = apothecary.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 APOTHECARY mean?
APOTHECARY noun- A person who makes and provides/sells drugs and/or medicines.
- A drugstore or pharmacy.
- A glass jar similar to those once used for medicine.