Losing head, trample marsh plant (4)
I believe the answer is:
rush
'marsh plant' is the definition.
(I know that rush is a type of marsh plant)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for rush that I've seen before include "Reed" , "Spate" , "Drug-induced euphoria" , "Hurry to the grassy plant" , "Be too hasty or too fast" .)