Re: When we say "Cleans", what do we generally mean?
The definition of clean and dirty has changed a lot over the years.
As guitar players, most of us wouldn't want 'hi-fi' clean. Even what old farts like me consider as a clean sound is coloured in desireable ways, e.g Fender or Vox cleans. Not distorted, but ... something magical and three-dimensional that the old tube amps have, like playing a 40-50 watt Fender amp quietly at home late at night with a good guitar.
In the 40 years that i've been playing guitar there have been huge changes in amps, sounds and the music that's been made. The dirty side of guitar sound has got dirtier and dirtier, and dirty guitar sounds have become more prevasive in more musical genres. Sometimes i feel that this has reflected on what people think of when they think of clean sounds (and of course there are probably some people who have absolutely no use for clean sounds, dislike them and wouldn't know what to do with them). Many of today's high-gain amps have compromised their clean sounds, and those that have sounds that can be called clean don't have much clean 'character'.
I blame it all on the advent of the master volume control, which, whilst serving the purpose for which it was designed, changed the musical landscape and amps in ways which diminished the quality of clean tones. I'm oldschool, and believe that all good guitar sounds are based on a good clean sound. But i know that i'm probably in a small minority, a dying breed, a dinosaur.