Double strike
Heroic — Whenever you cast a spell that targets Cleon, exile the top card of your library. You may play that card until the end of your next turn.
Cleon's second ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered or otherwise leaves the stack without resolving.
You pay all costs and follow all timing rules for cards played with the permission granted by Cleon's last ability. For example, if the exiled card is a land card, you may play it only during your main phase while the stack is empty.