Whilst I'm no expert - it doesn't sound to me like a copyright problem - after all, a film critic can publish their thoughts on a film they have no ownership of. The first concern that flashed into my mind though was - what if they delete the video? As you are not hosting it (or the owner of the youtube account) you have no control over whether part of your book is rendered somewhat unusable.
Is it a famous clip/something that several youtube users host versions of?
Can readers get enough value from your description, or do they have to see it?
Is it a famous clip/something that several youtube users host versions of?
Can readers get enough value from your description, or do they have to see it?