The most common and most likely answer to this crossword clue is the 8 letter word PURVEYOR
I've seen this crossword clue in Independent
P
U
R
V
E
Y
O
R
More clues leading to the result PURVEYOR
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 = purveyor.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 PURVEYOR mean?
PURVEYOR noun- Someone who supplies what is needed, especially food.
- An officer who provided provisions for the king's household.
- A procurer; a pimp.