"No, Tim is an actor, and not a medic."
Translation:Нет, Тим — актёр, а не медик.
The dash is a punctuation convention when there are two nouns that form the subject and the predicate.
"Is" is implied (there is no other interpretation here)—and, well, in English you cannot really omit it.
In Russian, though, "to be" is dropped in present tense sentences of this type (though, it is retained in declarations of existence of something and "I have"-sentences).