How do you delete just an Icloud Email address without deleting your entire Apple ID

You cannot delete the @icloud.com address you created when you first opened the account, nor its @mac.com or @me.com versions if you have these as a result of being a member of DotMac or Mobileme previously. You could open a new iCloud account with a different address without having to remove your exiesting Apple ID from elsewhere. However if you want a different address you can add up to three 'email aliases' - these are additional addresses (not accounts) which deliver into the same inbox as the main account. (In fact it's a good idea to give out alias addresses, rather than the main address, because if they attract spam you can easily change them.)

You should be aware before you start that once you've created an alias you cannot turn that address into a full iCloud account or move it to another account.

More information on aliases here: https://help.apple.com/icloud/#mm6b1a490a