Possible Clues:

• Interject
• Copper can interrupt speaker
• Don't wait your turn on a line
• Take over a dance
• Interrupt dancers, say
• Caught president losing head — failed to observe queuing etiquette
• Interrupt, as at a dance
• Jump the line
• Borrow someone's partner on the dance floor
• Interrupt ... or what to do as you enter the answer to the previous clue