Possible Clues:

• Crooked person accepting required incarceration initially?
• He can't leave one so nosy about my boy
• One who wielded a jemmy stops on being arrested
• Inquisitive person keeping child captive
• I'm inside right: little prince is one first
• Person in irons perhaps or vice versa
• Someone being inquisitive about boy who's inside?
• One is inside more likely
• Person behind bars
• He's held to be responsible for an offence