The phrase "a more significant question" is correct and usable in written English.
It can be used when introducing a question that holds greater importance or relevance in a discussion or analysis.
Example: "While there are many questions to consider, a more significant question is how we can address the root causes of the issue."
Alternatives: "a more important question" or "a more pressing question".
Or, to raise a more significant question, why did the city reopen the bidding process?
A more significant question is what made the NoW so vulnerable.
A more significant question hovers over the Explorer as well as the G.M. triplets: Is the public tired of trucks?
For policy makers in Washington, a more significant question than the actual date of the end of the current recession will be when to begin unwinding the myriad lending and guarantee programs that were hastily created in response to the crisis.
Arguably, that's a more significant question than the degree to which it's behind Tech Company X or Y in video, etc. Although, clearly, having added Katie Couric as an anchor, Yahoo is indeed serious — both about fixing video and competing with, well, someone.
I cannot remember when voters have had to answer a more significant question.
Benjamin took the more radical stand that the term "work of art" has no essential meaning; and concerning the "futile thought" that "had been devoted to the question of whether photography [or film] is an art," he observed that the more significant question had to do with whether such inventions "had not transformed the entire nature of art" (Illuminations 227).
While the case could be decided narrowly based on the unusual provisions of the city's ordinance, the court could rule on the more significant question of whether the 2nd Amendment protects carrying a gun in public.
But the broader and more significant question, he said, is whether or not an employer can require you to do other tasks deemed nonessential to the job -- for free.
