The most common and most likely answer to this crossword clue is the 7 letter word VENDORS
I've seen this crossword clue in The Sunday Telegraph
V
E
N
D
O
R
S
More clues leading to the result VENDORS
Buddy explains!

The straight part
We know that "sellers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sellers = vendors.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 VENDORS mean?
VENDORS noun- A person or a company that vends or sells.
- A vending machine.