These clues are all taken from definitions from dictionary.com.
Across
3. A person who repairs and maintains machinery or motors.
4. A person selected to rule on the plays in a game.
6. A person responsible for the interpretive aspects of a stage, film, or television production; the person who supervises the integration of all the elements, as acting, staging, and lighting, required to realize the writer's conception.
7. A murderer, esp. one who kills a politically prominent person for fanatical or monetary reasons. The word derives from a fanatical group, active in Persia and Syria from about 1090 to 1272, who ate cannabis before killing crusaders.
10. A person whose profession is inspecting and auditing personal or commercial accounts.
11. A person in charge of a museum, art collection, etc.
Down
1. A person professionally engaged in the design of constructions.
2. An academic rank given in colleges and universities to a teacher ranking below assistant professor.
5. Someone who watches examination candidates to prevent cheating.
8. A person employed by a government to obtain secret information or intelligence about another, usually hostile, country, especially with reference to military or naval affairs.
9. A female servant.
