As a general rule, a news site would be crazy to stop you from including a direct link to their news item in your RSS feed. If your RSS feed links to your own page, which summarizes the news story, it should be ok as long as you don't directly quote more than a snippet of the news site's copyrighted content, provide attribution, and link to the original page. This is very commonly done -- and encouraging links is in fact why many publishers provide RSS feeds.
To be fully legal, you need to check the terms and conditions for the RSS feed, which are probably linked from the page listing the RSS feeds.
