To prevent the portal from being crawled on a Google Search, you can have the following code attached under Portal customizations. This would available only for accounts on the Estate and Forest plans, though.
To hide the entire portal, please go to Admin --> Channels --> Portals --> Customize portal --> Layouts & Pages --> Portal Layout --> Head and add the below mentioned tag:
If you are looking to hide only the Solutions tab from being crawled, please paste the following tag-
{% if current_tab == 'solutions' %}
{% endif %}