Possible Clues:

• Where strain will cause a parting
• Last straw
• Pinot? That could be the last straw!
• I grip banknote (anag) — when a crisis is reached
• Ego-trip in bank sadly creates a critical situation
• Holiday in Galway on headland at a time when one is about to snap
• Moment at which something gives way
• Critical moment in back room summits for middlemen and a king? That's the nub!
• Critical moment
• Time of great strain