Scarlett
It just means there are 4 entries that, once you have made the alterations suggested by the song, are non-words. As it turns out, they are the answers to the clues with an extra letter inserted.
Xwordfan, you need a five-letter word for the first word (with an extra letter in it) in the clue. Take off the first letter of that, and you'll have a word meaning 'on record', permanent. Yes, it's one of the four.