If you have a regular stereo track, then it is no way this can be done. Some times it is possible to (partially) remove the lead vocal, since this usually is mixed dead center. When a number of recorded tracks are mixed down to a stereo file, then you have for instance stereo effects being printed all across the stereo spectrum. People who attempts to remove vocals will hear these vocal effects as a “ghost-like” voice in the background. The same will be true for a guitar track. Even if it was mixed dead center, you would still hear any stereo effects being used on the guitar (like reverb). What complicates the matter is that you almost always have guitars which are mixed right and left, doing the phase cancellation impossible to pull off. In order to have what you’re after, you will either need the original recording (master) and mix down from this – or, you will need to record a new version of the song, without the guitar.