Make Read Only a Custom Attribute CX Sales

1. A custom field is there 'Digital Priority' ( Fixed Choice LOV TYpe)
2. Client wants to make it Read Only and also want to update weekely via bulk import using CSV File Import Method.

So if i make it conditional 'Update' on App Composer for read only then it is getting error and not allowing to update. And Page composer is not allowing to do same.

I had code on updateable :-

if (1==1 )

return(false);

else

return(true);

So i need a solution where i can make this field it 'Read Only' and as well as can update via Import also.