Possible Clues:

• Closed with disgusted exclamation -- that is really hard puzzle
• Ireland behind strong, aggressive one
• Gout's boiling hot -- that is becoming a difficult problem
• Difficult question
• Violent criminal that's a difficult problem
• In match there's nothing that's nasty? That's hard to answer
• This water tester I'm disgusted one has broken
• Real head-scratcher
• See 19 Down
• Hugo tie designed for real hardchaw