Headlong rush of a group in panic (8)
I believe the answer is:
stampede
'headlong rush of a group in panic' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for stampede that I've seen before include "A flight of frightened cattle" , "Crazy pets made a sudden rush" , "Put to flight" , "Pasted me (anag.)" , "Sudden rush of frightened animals" .)