You can see in the screenshot below a spotlight suggestion that I don't understand why it shows up, it looks like a Safari icon (as a web search result suggestion), but it actually is a bit different. I don't understand where it came from, what kind of suggestion it is (file, web search, email?) and most importantly how do I get rid of it?
It is a Siri Knowledge tidbit, making a search to the web (presumably Wikipedia) about a general artist. Similar to if you typed the name of a sports team, Spotlight would intelligently return current stats and upcoming games.
In this example, I searched for another small artist, PTAF, where you can see a thumbnail of the artist is not displayed because there's not one available from their Wikipedia. When you search a more popular artist, a thumbnail is displayed.
In your case, Siri seems to have that random tidbit of information about that band without an accompanying Wikipedia page... nice