@finlamit You’ve described your relationships. So model them as such.
There are two belongs-to-many relations: actors belong to many movies, as well as belonging to many clips. So you’d need two pivots tables: actor_movie and actor_clip.
For the actor_movie table, I’d add a nullable column to store an alternative name in case the actor was credited under a different name. For example, Elliot Page was in X-Men: The Last Stand, but credited as “Ellen Page”.
You’d also have an actor_clip table to record the actors appearing in a particular clip, as the entire movie’s cast won’t be in every clip; you need to record the specific actors in each clip.