The phrase "a complex topic that" is correct and usable in written English.
You can use it when introducing a subject that requires detailed explanation or discussion, often in academic or analytical contexts.
Example: "Climate change is a complex topic that involves various scientific, economic, and social factors."
Alternatives: "a multifaceted issue that" or "a complicated subject that".
"It [the new paper] doesn't appear to add much to a complex topic that cries out for a large blinded, randomised clinical trial," he said.
"This is a complex topic that has raised a lot of anger, hostility, resentment and anxiety," said Dr. Leonard H. Sigal, the chief of the division of rheumatology at the Robert Wood Johnson Medical School in New Brunswick.
If you can begin to raise awareness for a complex topic, that's key.
Evolution is a complex topic that necessitates long-term exposure to comprehend fully.
Chemical similarity searching is a complex topic that lies at the heart of cheminformatics and can be carried out in a wide variety of ways to address a number of problems.
It's a complex topic that doesn't lend itself to soundbites favored by campaigns on one hand, shouldn't politicians be held to high standards?
With reference to the implication of the findings in regard to the advances to obtain a vaccine, we think this is a more complex topic that is beyond the purpose of this short research note.
Re-gifting is a touchy and sometimes complex topic that can readily turn a delightful gift exchange into an awkward and uncomfortable situation.
Status is a huge and complex topic that psychologists and sociologists are still trying to understand.
It's just four intelligent people in a studio, discussing complex topics that are, as a friend of mine once said of Bragg's openers, aggressively uncommercial.
There exists an inherent difficulty in imparting knowledge on complex topics that are difficult to grasp for medical students who often have had minimal exposure to direct patient care.
