The most common and most likely answer to this crossword clue is the 6 letter word DRIVEN
I've seen this crossword clue in Independent
D
R
I
V
E
N
More clues leading to the result DRIVEN
- Highly-motivated Democrat torn to shreds
- Compelled to redo Verdi composition, finally
- Ambitious study covering right current and velocity
- Ambitious Verdi composed opening for Nabucco
- Obsessive drip separates doctor and nurse
- Forced through split near top of duct
- Daughter torn apart, being highly motivated?
- Highly motivated household finally torn apart
- Taken for a ride?
Buddy explains!

The straight part
We know that "Ambitious" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ambitious = driven.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does DRIVEN mean?
DRIVEN verb- To provide an impetus for motion or other physical change, to move an object by means of the provision of force thereto.
- To provide an impetus for a non-physical change, especially a change in one's state of mind.
- To displace either physically or non-physically, through the application of force.
- To cause intrinsic motivation through the application or demonstration of force: to impel or urge onward thusly, to compel to move on, to coerce, intimidate or threaten.
- (especially of animals) To impel or urge onward by force; to push forward; to compel to move on.
- To direct a vehicle powered by a horse, ox or similar animal.
- To cause animals to flee out of.
- To move (something) by hitting it with great force.
- To cause (a mechanism) to operate.
- To operate (a wheeled motorized vehicle).
- To motivate; to provide an incentive for.
- To compel (to do something).
- To cause to become.
- To hit the ball with a drive.
- To travel by operating a wheeled motorized vehicle.
- To convey (a person, etc) in a wheeled motorized vehicle.
- To move forcefully.
- To be moved or propelled forcefully (especially of a ship).
- To urge, press, or bring to a point or state.
- To carry or to keep in motion; to conduct; to prosecute.
- To clear, by forcing away what is contained.
- To dig horizontally; to cut a horizontal gallery or tunnel.
- To put together a drive (n.): to string together offensive plays and advance the ball down the field.
- To distrain for rent.
- To separate the lighter (feathers or down) from the heavier, by exposing them to a current of air.
- To be the dominant party in a sex act.
- Obsessed; passionately motivated to achieve goals.
- (of snow) Formed into snowdrifts by wind.