The most common and most likely answer to this crossword clue is the 6 letter word PUSHER
I've seen this crossword clue in The Guardian
P
U
S
H
E
R
Buddy explains!
The straight part
We know that "dealer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dealer = pusher.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 PUSHER mean?
PUSHER noun- Someone or something that pushes.
- A person employed to push passengers onto trains at busy times, so they can depart on schedule.
- A girl or woman.
- A drug dealer.
- An aircraft with the propeller behind the fuselage.
- A device that one pushes in order to transport a baby while on foot, such as a stroller or pram (as opposed to a carrier such as a front or back pack).
- A defensive player who does not attempt to hit winners, instead playing slower shots into the opponent's court.
- A tolkach.