It's a kid's fantay movie. With an Evil queen/sorceress, trapped in a "tube" I think one of her hands was hit as the chamber/tube came down on her, imprisoning here within. I think she suffocates or is aging near the end of film;
I don't believe it's Legend, Labyrinth, Willow, or even The Never Ending Story. I think a brother and sister were the lead characters. It might be an adaptation of The Snow Queen, but I doubt that, too. 80s film, maybe earlier, can't be sure.

I just don't know the name of it. It bugs me.

I think what you're talking about is the hugga bunch.

She has a tree that grows fruit that keeps her young and she keeps it covered with the giant glass tube like think you're remembering, and at the end it is closing but the key s still under and gpes to reach for the key and her hand gets caught and she ages from not eating the fruit.

Hope I helped.