How do I clear up space ? I’m trying to back up

See:

If you can't back up to iCloud or if restore from iCloud backup failed - Apple Support

If an alert says that there's not enough iCloud storage

A message appears when you need more iCloud storage to back up (the available space on your iOS or iPadOS device is different than your available space in iCloud). Before proceeding, you need to know your Next Backup Size and how much iCloud storage you have available.

Here's how to find your Next Backup Size:

• On iOS 11 or later and iPadOS: Go to Settings > [your name] > iCloud > Manage Storage > Backups. Tap the device you're using.

After you check to see how much iCloud Storage you have, try these steps to complete your backup:

1. Upgrade your iCloud storage plan.
2. Reduce the size of your backup.
3. Delete any data that you don't need.
4. If you still need help, contact Apple Support.