Is there a song by the Beatles that has Just walk away in the lyrics?
No. "Walk Away Renee" was by the Left Banke.
The song containing these lyrics is not, in fact, a Beatles song - the song is "Day After Day" by Badfinger - included in their 1971 album Straight Up - there was, however, some Beatles involvement within the song, as it was co-produced by George Harrison. However, Harrison left the production incomplete, and it was completed by Todd Rundgren.