Possible Clues:

• Out-and-out
• Fixed and uncom­promising
• Yet when old I do fancy being of fixed opinion
• Incurable oldie they'd now treated
• Hardened criminal with old doyen swallows Ecstasy
• Unchanging in a particular belief
• Wheel tiny dodo out -- it's incurable
• Fixed in one's opinions or attitudes
• When shot, do they lie down? That's confirmed
• Hard-core red, maybe wearing sheep's clothing?