From Console:
1. Sign in to the AWS console.
2. In the console, select the specific region.
3. Navigate to the ‘Redshift’ service.
4. Click the identified Redshift cluster name.
5. In the top menu options, click ‘Cluster’ and choose ‘Actions’ as the option.
6. Click on ‘Modify Publicly accessible setting’ option.
7. Choose ‘enable’ option and click ‘save changes’.

From TF:
resource aws_redshift_cluster” “test”{
cluster_identifier = “tf-redshift-cluster”
database_name = “mydb”
master_username = “foo”
master_password = “Mustbe8characters”
node_type = “dc1.large”
cluster_type = “single-node”
+ publicly_accessible = false
}

From Command Line:
To Disbale ‘Publicly-accessible’ Run:
aws redshift modify-cluster –region us-east-1 –cluster-identifier redshift-cluster-1 –no-publicly-accessible

References:
1. https://aws.amazon.com/premiumsupport/knowledge-center/redshift-cluster-private-public/