Drive off in Open, go too far? (9)
I believe the answer is:
overshoot
'go too far?' is the definition.
(to overshoot is to go past)
'drive off in open' is the wordplay.
'drive off' becomes 'shoo' (shoo can mean to drive off or send away).
'in' indicates putting letters inside.
'open' becomes 'overt' (synonyms).
'shoo' put inside 'overt' is 'OVERSHOOT'.
(Other definitions for overshoot that I've seen before include "Maybe miss the green" , "Go beyond the mark" , "Fly beyond" , "Go extra distance" , "Go past unintentionally" .)