Possible Clues:

• Excessively virtuous person
• Ostentatiously nice sort
• Excessively proper person — killjoy
• Well-behaved person
• Prim and proper virtuous type
• Dot's gooey show? (anag)
• Prim and proper one
• Prudish sort
• Pious female convert who goes to synod – not new
• Someone who's so nice you almost want to smack him