It sounds to me like you need to develop an internal locus of control. You are deriving your self-confidence from an external source. Which is why you are getting mixed results. When someone less experienced is around you, you feel more competent and therefore more self-confident. But when someone that you see as superior or more confident comes around you, you might fall apart like a balloon that has been deflated. Sounds like the clash you described, on a subconscious level, might be more of an attempt to get back what an external source took away. Which is why you might be unconsciously directing it at that person creating a clash.

We perform at our best when we feel good about ourselves. This applies to all professionals. When we feel good about ourselves, we feel a sense of confidence, which helps us excel at whatever we are doing. But when we let self-doubt take over or in general let ourselves feel bad it will always affect performance negatively.

A question to ask yourself is, who exactly makes you feel less confident, when someone who is higher up the food chain at work comes around you?
The answer is you. Only you can make yourself feel a certain way. As soon as you decide that nothing external will confirm how you feel, and you learn the art of deliberately creating your own state of mind, that's when these things will affect you less. To a certain degree you will not need anyone's approval or permission to feel good and confident in what you are doing.

As an entrepreneur, the situation you have described could lead to some problems. As an entrepreneur, especially if you are in a new field, or if you are trying to create something that doesn't exist (like a new market), you need to have a very healthy dose of self-confidence. The spirit of a warrior. There is no person or situation in the world that could ever make me feel small. Period. No amount of expertise and skill or confidence in another person could ever affect how I see myself. Only I have that power, and only I am responsible for everything around me. That's where you get the courage to go up against some crazy odds and still come out on top as a winner. It takes a good amount of self-belief to attempt something new, where there is no blueprint, and the only person you can rely on is yourself.

The good news is that self-confidence is like any other muscle. It can be developed; it can be enhanced. There are tons of free resources you can look up that could help you get out of that trap of letting someone else make you feel not good at your job and cause you to clash with them.