Possible Clues:

• I'm in the slit in the end
• See 17-Across
• Holds in check around Limerick in high spirits
• Can't go beyond them to make it slim for them
• 'Boundaries, demarcation lines (6)'
• Vegas table postings
• Puts a cap on
• Beyond them it's no go to have it in so slim a way for them
• That's as far as I'm able to get in the slit
• I'm in the lists at last