Amy sings "lickle carpet burn". ickle is london slang for little, pronounced lit-all with a cockney account. This gets changed to lickle and sometimes even ickle meaning small.

People think it refers to sex. I think it is a needle mark. Rug burn is another slang for this and in the UK carpet would also be used for rug. But watch the video, when she sings this line, the guy playing her fella, picks up her arm and looks at the lower inside of it, then drops it shaking his head. Seems like a clear reference to needle track marks to me.