This achievement is gained for destroying all enemy units in the village while avoiding collateral damage. The mission is triggered after discovering the village at the beginning of the mission. Use your Hellfire's and hover while using your gunner manually to avoid hitting friendly units!
The exact mission description reads: "Destroy enemy vehicles leaving the village. Avoid collateral damage." It is the second mission objective in the level "Sunshine Units". This achievement is campaign related and cannot be missed.