How can I clear the Safari browsing history from a child's phone?

I set up parental controls on my little brother's Iphone and Ipad at the request of my mom. To make sure it was working the way it's supposed to, I opened Safari and searched an explicit word. The search results were blocked, which is great, but the search itself was still in the browsing history and when I started to type a word with the same first letter the explicit word came up. I obviously don't want the explicit word to come up every time he tries to search a word with the same starting letter, because then that word will be in his face every time and that defeats the purpose. The "clear" button is grayed out since content restrictions are turned on, so how can I get rid of the search history?