if one seat is remaining for admission .why we will give it to you?

They don't want poetry. They want an essay. Please write what they want you to write. Otherwise you just prove you can't follow directions. Please don't hurt your chances that way.

I am not saying that I will write poetry rather the essay topic is asking about my potential so if I only mention this potential so how will it be related in getting admission.

You don't understand what this application question wants to find out.

Here are some things you should talk about. Yes, your poetry can be included but how will it help you be a better student?

Are you a hard worker? Are you organized? Do you enjoy learning? What talents do you have that can help your studies? Does your damily support your efforts? Are you friendly and can work with others? Are you in good health? Why do you want to go to this particlar school?