Adding a second email to iCloud

Add and manage email aliases for iCloud Mail on iCloud.com - Apple Support

If you're referring to an additional email address (something@icloud.com), the answer is yes.

You have two options:

1. Add an alias email address, which forwards all emails to your main account.

2. Sign up for an additional iCloud account.

However, having multiple iCloud accounts can get confusing. For example, apps downloaded from the App Store are tied to the account used to purchase them. This means you'll need to log into the appropriate account to update those apps, or the update may fail.

Create a primary email address for iCloud Mail - Apple Support (CA)