It's actually two words: tar baby.
tar baby
tar ba·by (plural tar ba·bies)
noun
Definition: tricky situation: a very troublesome situation, especially one that is difficult or impossible to get out of ( dated )
[Early 20th century. < the Uncle Remus story Brer Rabbit and the Tar Baby by J. C. Harris]
I realize you were waiting for RSR for the definitio, but I thought I would help move the conversation along.
I remember my father reading to me from the Uncle Remus story book when I was a kid. It was a wonderful collection of stories. I have never considered the term "tar baby" to be racist, but I am not black. It seems to me that a person would have to be very sensitive to think the term racist. But again, I am not black.
The Disney classic Song of the South used the stories of Uncle Remus, I always thought it was a very good movie. One of the first uses of animation and live action, groundbreaking for it's time. Interestingly, you can not buy Song of the South in the United States. Why? Primarily because of the segment of the film containing Brer Rabbit and the tar baby. I believe there are some who think the are other racial undertones in the rest of the film as well.
Again, I have never thought of the stories, film or book, or the term "tar baby" as racist. They have always been a means to convey some life lessons to children, not indoctrinate them into a life of racial hatred.
But, I'm white. What do I know?