Headlong rush (8)
I believe the answer is:
stampede
'headlong rush' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stampede that I've seen before include "Sudden rush of people" , "Chaotic rush" , "rush for safety maybe" , "Sudden dash of a group of startled animals" , "Headlong rush of a group in panic" .)