Watch the Clean Comp Lead online guitar lesson by Jeff McErlain from Guitar Effects Survival Guide
I am channeling Jeff Beck on this effect chain as well as David Gilmour. A compressor can do wonders for a clean sound, especially when playing lead. It'll give you a nice punch to the notes as well as increase your sustain. The reason for this is because compression gives you many of the characteristics of playing with an over-driven tone but without the overdrive. Excellent examples of clean compressed lead tone are "Where Were You?" by Jeff Beck and "Another Brick in The Wall Pt 2" by Pink Floyd.