Possible Clues:

• Collision after last of vehicles suddenly appeared
• Bound to have pressed the bell at last enough to have made one jump (6)
• How the bell went off at last, as was repeated
• Leapt foward
• Lept forward
• Jumped up, getting the latest information, and phoned
• Jumped up to grasp clumsily and the point penetrated
• Developed a leak, perhaps, after the second accident
• Suddenly leapt (up)
• Second bump suddenly developed