Brief encounter, throwing first dart (4)
I believe the answer is:
rush
'dart' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for rush that I've seen before include "Stampede - marsh grass" , "Hurry to the wetland grass" , "Race" , "Hurry, surge" , "Hurry - marsh plant" .)