Any way to un-muffle an .mp3?

A nice older lady I know has asked if I can do anything with a song she recorded, of a friend of hers singing, I think on her cell phone. She moved her finger on to the mic early in and it becomes muffled -- still audible and distinguishable, but definitely muffled. I'm not a sound guy but told her I'd "see what I could do," and this is it.

Any recommendations? I have no idea even where to begin!