Fail suddenly (8)
(Other definitions for collapse that I've seen before include "Abrupt failure of function" , "fold" , "Suddenly fall down or give way" , "Fall or disintergrate" , "Break down - fall" .)
(Other definitions for crash that I've seen before include "Collide violently" , "Violent collision" , "Planned quickly for emergency" , "Car accident" , "Dramatic fall" .)