Possible Clues:

• Rule of thumb
• In deluge I recollected recommendation
• Lead Neil at sea, giving indication of course to be followed
• Recommendation of good Scottish priest born in Paris
• House style, say, covering variant spelling of i.e. 'dueling'
• Rule of thumb — need Luigi (anag)
• General piece of advice
• One may follow this river northwards when in control
• Advice on general policy
• General rule