A guitar 'lick' is a slang expression which can either be used to denote a solo, or the first statement of the melody of the song - also referred to as a 'riff''. It's a fairly loosely used word, as musicians' expressions often are, when referring to the finer points of their craft. One intriguing use of the expression was to use it as a band name - Dan Hicks And His Hot Licks which is probably intended to imply the quality of the music produced.