Possible Clues:

• How those with 1 across might put the fowl in the oven
• Person lacking culture or moral principles
• Get the fowl hot to an unbelievable extent
• Warm weather for one getting married to one who doesn't have 27 down for instance
• Let's not have bird shivering: it's uncivilised
• Target of proselytizing
• Irreligious basics for preparing roast chicken?
• Let's not have cold chicken — it's uncivilised
• Pagan: let's not have cold chicken!
• Male with endless capital, not one of the faithful