Possible Clues:

• Chopper (spelled backward) + Gold digger = ?
• One administering test
• Investigator cut up over someone getting blackened
• Marksman? Formerly a collier
• Formerly worked underground, now has more testing employment
• One's work makes one very testy
• I name Rex mistakenly as analyst
• Formerly an underground worker, now has more trying work
• I'm 'ere with an X - if you get it all wrong!
• Formerly employed in the Underground, now in more testing employment