What do we call somebody who...?

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Across
  1. 2. participates in something?
  2. 4. instructs other people?
  3. 5. works in chemistry, or studies it?
  4. 7. supplies something?
  5. 9. works in a library?
Down
  1. 1. drives a motor vehicle?
  2. 3. seeks refuge from a disaster?
  3. 6. survives an accident?
  4. 7. specialises in something?
  5. 8. presents a TV show?