Unionists only here on a Sunday perhaps? (6,4)
I believe the answer is:
closed shop
'unionists only here on a sunday perhaps?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
This is the entire clue.
Can you help me to learn more?
(Other definitions for closed shop that I've seen before include "factory where all the workers are unionists" , "only the unions were taken in" , "Shut down business" , "Union bastion" , "Ceased trading" .)