Translation:The Secret Service had to answer for the safety of the president.
"To answer for" something is an English idiom--and apparently a Spanish idiom as well--for assuming responsibility for something and taking the blame if you fail to do so. In other words, the Secret Service (which is an American entity tasked with safeguarding the president, part of the Treasury Department for some weird historical reason) has to take responsibility for the security of the president and will take the blame if the president gets killed. It's a perfectly normal idiomatic English sentence. Whether it's an equally normal Spanish sentence I have no idea.