Have you done similar things before? What are the steps you took?
The most likely outcome of your idea is that you will work hard, launch, and discover then that actually no one is interested and at that point you discover why.
When talking about ideas to others you will discover that: - Most people have their own ideas that they think others want to steal and that they think are much better ideas than yours. (You'll think these ideas are worse than your own.) - Most people will think the idea sucks. (it's natural, just like you'll think their ideas suck)
There's a lot of information needed to be able to understand an idea. That's why you should also just validate the problem you are solving or some part of it, or part of the solution. You can't validate the whole thing. "Would you use this product" is the wrong question.
So you can be pretty comfortable in asking feedback.
However.
Get feedback from people who are relevant to the target audience.
Get feedback from people who are already invested in something. I wouldn't necessarily validate with a serial entrepreneur that's looking for something new to build. Although the more likely outcome is that he'd want to work with you which would be the best outcome for you.
Get feedback from people who don't have a significant advantage compared to you to get it done.
You shouldn't be afraid of competitors. They will come anyways. You should be confident in your ability to outperform them - you will have to. Which also means that these people you are validating with that you think could steal your idea - you need them on your team. Or you need to build to a team so strong that them stealing doesn't matter. You still actually need to build that team.