Possible Clues:

• Feeling of discontent when messenger drops round
• Sin often associated with green
• English sailors without a feeling of discontent
• Resent heads of exiting nations vacillations year-on-year
• 'That most odious and antisocial of all passions': John Stuart Mill
• Sin that sounds like two letters
• Wishful thinking?
• Green-eyed monster's emotion
• That ''green'' feeling
• Desire to have something that is possessed by another