Restrictive trade union forced store out of business (6,4)
I believe the answer is:
closed shop
'business' is the definition.
(closed shop is a kind of business)
'restrictive trade union forced store' is the wordplay.
I cannot really understand how this works, but
'union' could be 'closed' (similar in meaning) and 'closed' is found in the answer.
'store' could be 'shop' (synonyms) and 'shop' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'out of' is the link.
Can you help me to learn more?
(Other definitions for closed shop that I've seen before include "Exclusive workers" , "firm with restrictive hiring policy" , "Ceased trading" , "where union holds sway" , "factory where all the workers are unionists" .)