Possible Clues:

• Not a person immune from criticism, but sounds like it
• Cask of wine is hit with head
• Fag-end for bum...
• You might grind it out
• Object of scorn, of humour
• Bottom, where water collected, perhaps?
• Thing in an ashtray
• Water-cask; object of derision
• Hit with the head; cask
• Hit with the head, as a goat