Possible Clues:

• Remunerative
• Pilfer boat (anag) – lucrative
• Endless difficulty framing suitable answer that's useful
• Seems it pays for one to come between the professor and the one he's sitting at
• Academic, one sitting on the board making money
• Useful person with chair and one other piece of furniture
• Rewarding
• Cost-effective
• Rewarding suitable answer in endless puzzle
• Person with chair, one piece of furniture that's useful