Sudden movement (5)
I believe the answer is:
lunge
'sudden movement' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lunge that I've seen before include "Thrust, sudden pass" , "Make a thrusting forward movement" , "Sudden thrust forward" , "(Make a) forward thrust" , "Trust forward as with sword" .)