Kill off new growth (5)
I believe the answer is:
shoot
This might be a double definition.
'kill off' is the first definition.
'shoot' can be an answer for 'kill' (shooting is a kind of killing). I am not certain of the 'off' bit.
'new growth' is the second definition.
(a shoot is new growth from a plant)
Can you help me to learn more?
(Other definitions for shoot that I've seen before include "big game expedition?" , "Fire (a gun)" , "away" , "Film; move rapidly" , "Fire - new growth" .)