Mark is correct, however that does not mean that there is not a way around this TOS where you are still in good standings with hubpages. What I mean by this is that you can still promote the clickbank products, but what you need to do instead of just putting up your clickbank affiliate link is this:
1. Pick a product to promote
2. Create your own sales page or squeeze page that promotes the title of that product.
3. Upload that squeeze page or sales page to your own domain name.
4. Use that URL that you have just created in your links that hubpages allows you to have. I believe that you are able to use two links that are outside promotional areas in your hubs. Not sure, but just ensure that you are following hubpages TOS so that you are not violating any of their policies.
This process may take a little bit more time for you but it will allow you to legally promote your affiliate products from clickbank on your hubs without violations to any of your hubs.
I hope that this helps out some!