The phrase "a definitive one" is correct and usable in written English.
It can be used to refer to something that is conclusive or final, often in the context of a decision, answer, or statement.
Example: "After much deliberation, we reached a definitive one regarding the project's direction."
Alternatives: "a conclusive one" or "a final one".
Certainly Crawford's new beginning is a raid on the forced inarticulacy of past ventures, and likely to prove a definitive one for some time to come.
That's more of a hopeful statement than a definitive one.
Diana Krall is a talented singer and pianist, but a definitive one?
And it becomes clear that his struggle to fit into his surroundings has been a definitive one.
In addition, the plan proposals I recall (though there was never a definitive one) involved putting aside some portion of future contributions into an account rather than scrapping the current plan outright (we still must pay benefits to existing retires).
StatCounter is an interesting barometer for Internet trends — it was among the first to signal that Chrome had become the world's most popular desktop browser — but its data represents a (large) snapshot of the total web not a definitive one.
That quip would once have irked Neville as a definitive one-club man in the 20 years he spent at Manchester United.
In general, the conclusions of the work should be toned down, outlining the complexity of the problem and how this work offers a possible answer, not the definitive one.
For too long, Republicans have claimed to have the monopoly on patriotism and consider their jingoistic definition of patriotism to be the definitive one.
Now, of course, every injustice needs a protest song, and Jimmy Fallon wrote the definitive one: "Balls In Your Mouth," which he debuted last year.
Until we can give a definitive answer one way or the other, I think we should respect that.
