Hi. I’m Japanese high school student.
“脇役” means a person doesn’t play a main role in the story. It’s used when you want to describe something don’t stand out.
“霞”is a kind of whether. Maybe “misty” or “ hazy”.
When it’s hazy, you can’t see anything, right?
So “脇役に霞ませる” means to make something out of your attention in this text.
I guess This text is from a novel.
Novels have lots of unique expressions. Good luck