Steve,
"Flem" is a term used for the mucus one gets when they have post nasal drip from their sinus cavity drain down into their throat. (Now isn't that a nice image... :-))
As far as eliminating it from a vocal recording, I seriously doubt it's possible. Mainly because it's probably occurring at the same time a note, or pitch is occurring. You can't eliminate one without eliminating the other.
That's the kind of stuff that needs to be addressed while recording, not afterwards. However, depending on the vibe of the song, it can severely add in the believability factor, as long as it isn't causing the attention to drift from the sung performance.
Is it just a little bit, and you've become obsessed with it, now that you hear it, or is it truly distracting?
Is it from a section of the song that is repeated elsewhere, and can be flown in place of it?
Wish I had the magic trick, but there really isn't one that I know of....