Possible Clues:

• Compulsory
• Required
• Your man the Da just has to be Conservative
• It's de rigueur to be male and right-wing
• Unavoidable day matron goes mad
• There's an obligation to make the fatherly fellow conservative
• Standing eight count
• Your old man has no option but to be a Conservative
• Combination of spy chief and a politician required
• It's essential for that fellow, Father, to be conservative at last