How do you destroy a clone ?c#

hey guys i need some help with trying to destroy these clones after a certain period of time. i need them to be destroyed so that there isn’t a clutter of them. here is my script. the script is attached to what is being cloned.
thanks for your guys help

public class destroyenemy : MonoBehaviour {

private float timerfive;

void Start () {

}


	
// Update is called once per frame
void Update () {
timerfive += Time.deltaTime;
if (timerfive > 3)
	{
		Destroy(gameObject);
		
	}


}

}

you can use Invoke:

function Start(){
Invoke("DestroyIt",10.0f);
}
function DestroyIt(){
Destroy(gameObject);}

attach that to the object prefab, it automatically gets destroyed after 10s

void Start(){
    Invoke("DestroyIt",10.0f);
}
void DestroyIt(){
    Destroy(gameObject);}