The issue is the white portion you are referring to is painted white in whatever application you have used to create the clothing.
If you want to see your character’s skin you will need to set those areas to transparent.
I will provide an example of what I mean momentarily.
Edit: Here is an example of how to test if your transparency has worked:
As you can see, I have uploaded the design as a T shirt, and I can see the shirt my avatar is wearing, which means the transparency is working correctly.
If you need assistance, I can send you the copy of your file that I have edited, and if the issue persists, it might be caused by your package/rthro