The community page is the landing page for both you and your clients. This means it's the first thing they will see when they log onto your portal. In the community, there is a special message box. By standard, you and your clients can both post messages that will be seen by all the members of your club. But since the default email settings for every client are that they receive an email when a new message is posted, you might want to disable this option for your clients. This way, you make sure your clients will only be emailed when an important message or blog is being posted. Your clients can still post replies to every post, so they will be able to ask questions or participate in a discussion topic.
To change the group settings; who can post, receive emails when a new post is made etc. Select the "Edit group information" and from there you can adjust the settings as you see fit.
If you think your clients would like to be able to talk to each other through your portal, you can create an extra group in which everyone is allowed to post messages. Just click on "groups" in the community and choose "create a new group".