Like a book or website?
I haven't come across great enmeshment specific resources. But I did really like the book Will I Ever Be Good Enough? By Karyl McBride. She is focused on the mother-daughter relationship and it encompasses a wide variety of toxic behaviors. It's been awhile but I do think she covers enmeshment. Hopefully some others have some enmeshment-specific resources.
Sharon Martin LCSW writes about enmeshment. I have only read articles but I believe she wrote a book.
Try also "Mothers Who Can't Love" by Susan Forward
There is information in there about enmeshment.
You can find it free if you google "mothers who can't love pdf" and it will bring up pdfdrive. Use the preview function and you can pretty much read the whole thing.