Possible Clues:

• Bin operator (anag) — one's working on a trial basis
• Struggling in art, be poor apprentice
• Professional baritone upset one being tried out
• Tester of a person's conduct
• Novice backing baritone is worried
• One on trial in post
• Offender on conditional release
• No amateur cricketer, I! One getting runs as young professional?
• New employee - one under legal supervision?
• Novice transformed into a penetrating researcher