The Smartweb / Hostedshop feed allows you to filter away or include out-of-stock products easily, by changing a simple part of the feed URL.
In my.clerk.io, go to Data Sync.
Make sure that the URL ends with
Then click Update Settings and Start Sync to load all of your products to Clerk.io
When importing all products, including out-of-stock ones, you will get the attribute in_stock available for all products, so you can filter some Clerk.io element, to not show these.