Points worth considering:
Intro: Terrorism has been around for a long time – going way back to 105 BC as state terrorism during the French government’s Reign of terror – and while terrorist groups and acts have been eliminated over the years, we’ve always seen new groups and acts of terrorism crop up.
Thesis: That individual terrorist groups might be eliminated (e.g. Tamil Tigers), but as a concept, because new groups will keep cropping up, as they have throughout history (these reasons will anchor your body paragraphs), the elimination of terrorism as a concept is not a realistic aim.
Body: One body paragraph could consider how characteristics of modern society (e.g. globalisation) both helps and hinders the elimination of terrorism (helps both terrorists and those fighting them)
Conclusion: Even though it’s not realistic, this doesn’t mean we shouldn’t continue fighting terrorism, or that we shouldn’t aim to eliminate individual terrorist groups as and when they crop up.