This is received randomly, where a Governor will ask for your help in taking over another faction's port through exposing another Governors misdeeds, using the daughter as leverage.
After accepting the mission, head to the port and win the staged kidnapping of the daughter, which will result in you gaining the Governors trust and meeting them again for dinner.
You will have to convince the daughter to head out of the complex. Once outside, be sure to select the dialogue where you accuse her father of taking part of illegal actions. Afterwards, she will leave you. Return to the Governor that gave you the mission and report the success. This will unlock the achievement.
If you choose the other dialogue instead, you will end up marrying the daughter, failing the mission and the achievement as well.