Swoop (6)
I believe the answer is:
pounce
'swoop' is the definition.
(I know that swoop can be written as pounce)
This is all the clue.
(Other definitions for pounce that I've seen before include "Strike" , "Spring down on and grasp" , "Spring to catch" , "Spring or swoop down on to attack" , "(Of cat) sudden leap to seize prey" .)