An event or situation ensues when it happens as a result of another event or situation. Think about what happens after a big storm hits your town - chaos might ensue.
We often use the word "ensue" to talk about consequences or results that follow something else. For example, if you spill food on the carpet and then the stain becomes hard to clean, the mess that's difficult to remove could be said to ensue from the original spill. If a school decides to cancel classes due to a snow day, the students might get bored and lazy - their behavior could be seen as ensuing from the lack of structure provided by school.
To follow (a leader, inclination etc.).
