An aircraft in "clean" configuration means that landing gear and high lift devices (flaps) are stowed.
Almost all pictures on other web sites are not "clean" but "dirty" configuration.
I like "clean" rather than "dirty", because "clean " is "KIREI" in Japanese which also means "beautiful".
So I take pictures of aircraft in "clean" configuration.
These pictures are aircrafts cruising about 10000m high over Hamamatsu city in Japan.