Depends on what you mean by "clean amp." If you mean clean but still with the volume up enough to get the power tubes and speaker cooking a bit, then the world is your oyster. Most every classic OD pedal will sound good in that situation, it's just a matter of taste (do you want boosted mids? bright? warm? etc). But if you mean a clean amp that isn't being pushed, then I would probably go with an amp-in-a-box type pedal in that situation. Catalinbread and Wampler both make some good ones. I think most of the popular OD circuits need a pushed amp to sound really good. Need is maybe a bit too strong a word. But they don't sound as good unless the amp is being pushed.
I have to say it's the one I recently finished building from a kit
A KOT clone - the "Two Kings" pedal
I built it with the "high gain" option on just the "red side" or right side of the pedal, so I can get anything from a hint of clean boost to full-on distortion - all out of one pedal, and it's all good tone - nothing fizzy or fuzzy about it
I don't claim to understand exactly how it works (it has a ton of resistors, caps, diodes, transistors, etc) but it doesn't detract from, or change the sound of your guitar and amp - it just enhances it
It works great with the Fender amps I've run it through as well as through my Mesa and Orange
It replaces the handful of boosts and over-drives that I've accumulated over the years
* For an equally good pedal without distortion capability, I'll go with the Ghost pedal - it's a clone of the Klon - it sounds fantastic running through a clean amp - very similar to the Two Kings in the way it doesn't change the character of the guitar and amp - it just enhances it
I really like the Greer Lightspeed or Strymon Deco tape saturation section into clean Fender-type amps. I don't need an OD to be super-transparent (in fact, I like it when they have a little bit of character), and both of those do a good job of heating things up without totally changing the tone.