Clue: Fogey briefly holding these people under detention to begin with (5-2-3-3)
Answer: STICK-IN-THE-MUD
Explanation: Fogey briefly holding these people under detention to begin with (5-2-3-3)
**STICKIN**(g) (*briefly* "holding) + **THEM** ("these people") + **U**(nder) **D**(etention)