You mean outside, it's not part of something. person who works very circumstantially on a film, which is not part of the cast. It also means supplement, supplement, added, additional.
1st_ Apocope of extraordinary . 2o_ It says of what is added . 3rd_ It is said to qualify as a superior. 4th_ Supporting actor, usually without parliament, who completes or does number in a scene. 5th_ Extra- prefix .
Extra: (adj. ) Extraordinary, which is higher than normal quality, excellent.