do you to apply for a licence to use a snippet of a song as background music to a short film?

It's going to be an animated film. I wrote one script for a story about Christmas. I know a particular contemporary Christmas song that would be perfect and has the same message about the story. The film will end up being much shorter than the total song.

Actually my brother wants to make the animation and it would then be published on his you tube channel. I've finally tracked down the record company that released found o the song. However, I'm wondering, is this actually worth applying for a licence? What kind of licence would I need?

I can't actually find any information on their website about what the copyright includes, but I can find a system where you can select what kind of licence you want and fill out a form online.