Go too far, having finished with new growth (9)
I believe the answer is:
overshoot
'go too far' is the definition.
(to overshoot is to go past)
'finished with new growth' is the wordplay.
'finished' becomes 'over' (over can mean finished or ended).
'with' means one lot of letters go next to another.
'new growth' becomes 'shoot' (a shoot is new growth from a plant).
'over'+'shoot'='OVERSHOOT'
'having' is the link.
(Other definitions for overshoot that I've seen before include "Go past unintentionally" , "Go extra distance" , "Go beyond the mark" , "Go past the mark" , "fail to stop where intended" .)