How should I handle students who ask questions that are "beyond the scope of the course" as a TA

One of the most common replies I have gotten as a student in engineering is the phrase "what you are asking is beyond the scope of this course". But I always found it a bit funny coming from the prof since he or she most reasonable have a thing or two to say about the subject. Furthermore, whether something is considered "beyond" sometimes depends on a prof's temperament, on a good day a topic that is beyond will be addressed, or a busy day that topic is hold off indefinitely.

Now I am a TA for an introductory calculus class. Often there would be a handful of students come into the class with years worth of experience in calculus. Sometimes they will ask a question that is addressed in an upper year course, sometimes the question would have to resort to complex variables, sometimes it relates to physics.

How should I handle students who are interested but asks question beyond the course in the sense it requires an additional course or two to truly appreciate its importance or at least to see how the actual calculations are performed.

I could tell them the answer but sometimes it can lead a student down a rabbit hole which can be devastating given how busy first year students are.

Further, I don't want to disrupt their "natural course" by saying something that may prevent independent self discovery.

Lastly, I don't want to say something which could be misconstrued as a test topic.

At the end of the day, how should I address the questions that are deemed beyond the scope while not withhold information.