The most common and most likely answer to this crossword clue is the 8 plus 8 letter word USED-CAR SALESMAN
I've seen this crossword clue in The Guardian
U
S
E
D
-
C
A
R
S
A
L
E
S
M
A
N
Buddy explains!
The straight part
We know that "Dealer stereotypically" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dealer stereotypically = used-car salesman.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.