The most common and most likely answer to this crossword clue is the 6 plus 4 letter word CLOSED SHOP
I've seen this crossword clue in The Guardian
C
L
O
S
E
D
S
H
O
P
More clues leading to the result CLOSED SHOP
- Employment system brought an end to trading
- School’s dep. sacked where union holds sway
- Get rid of officer during cut in firm with restrictive hiring policy
- Demand of union prevented trader doing business
- Stopped selling members-only arrangement
- In which only brothers and sisters are employed?
- Company with limited employee system finished business for the day?
- Union bastion holds scope for redevelopment
- & 25d Staff organisation that prevents trade?
Buddy explains!

The straight part
We know that "Demand of union/prevented trader doing business" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case demand of union/prevented trader doing business = closed shop.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.