Export iCloud items from Keychain to CSV
A late reply, as I found this post while searching for something related.

You have to create a new keychain, and copy your iCloud keychain items to the new local keychain.  Then you can use the security tool to dump them.

Since this is 1Password-related question, for others in the future, you can use MrC's conversion utility to directly convert the keychain dump into a 1Password consumable 1PIF file.  It is much better than CSV importing.

https://discussions.agilebits.com/discussion/30286/mrcs-convert-to-1password-utility/p1