1. An operation or concerted effort to clean or tidy some large area or thing. Now that the festival is over, the city is organizing a massive clean-up operation to return the streets to their former state. Following the spill, the oil company was court-ordered to pay for a clean-up operation for the entire region.

2. Any action or procedure meant to cleanse, eradicate, or resolve any final or lingering loose ends. We've gotten most of the hard work done for the merger—we'll just send our legal team through our accounts on a clean-up operation to make sure everything is in order before the move is finalized. The dictator began a massive clean-up operation after assuming total power, sending troops throughout the country to round up and execute any remaining dissidents.