How can i delete an incomplete movie download on ipad air?

I used the app "12 presents" that gives the user everyday a new present that is only downloadable on this very day. One of these presents was a movie track I started to download. But unfortunately my internet broke down and so the download kept incomplete. Since you cannot download the present on the next day, there is no way to complete it now.

Thus I can see the incomplete movie in the movie folder but I cannot open and watch it. Therfore I want to delete it - which is also not possible. There is no delete or change button whatsoever.

I use ipad air.

I would be thankful for any ideas. Maybe I'm not the first one to have this problem.

Thanks!