[krastanov]

Entropy always increases in a closed system. Entropy of a part of a system (i.e. an open subsystem, e.g. the Earth) is a well defined quantity (it is even a thermodynamical potential, hence completely independent of the history of the system, only dependent on the current state) and can be decreasing (and even the most basic thermodynamics textbook has plenty of examples).

And yes, the entropy of Earth is decreased by cleanup efforts. Only when including the Sun you get a system in which the total entropy increases. But this would be quite useless thing to do, given that the Sun is an infinite source of energy for practical purposes.