I am going to point you to the
Creating an App Clip with Xcode documentation, specifically, the
Keep Your App Clip Small in Size section. This section has a great tip for for exporting your App Clip from Xcode, and how to see the App Clip's uncompressed size.
Succinctly, you can export your App Clip by "archiv[ing] the app clip’s corresponding app, open the Organizer window, select the archive, and click Distribute App." Then, you can "[e]xport the app clip as an Ad Hoc or Development build with App Thinning and Rebuild from Bitcode enabled."
Upon exporting, in the output folder you chose to export to, you will see a
Thinning Size Report.txt file. This file will include the uncompressed size of the App Clip, which you can use as a guide for trying to ensure your App Clip fits under 10MB.