Employment system brought an end to trading (6,4)
I believe the answer is:
closed shop
'employment system' is the definition.
'to trading' is the wordplay.
'to' becomes 'closed' (I've seen this before).
'trading' becomes 'shop' (I am not sure about this - if you are sure you should believe this answer much more).
'closed'+'shop'='CLOSED SHOP'
'brought an end' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
(Other definitions for closed shop that I've seen before include "where union holds sway" , "Where union membership is required" , "Union bastion" , "factory where all the workers are unionists" , "Ceased trading" .)