Definitions of unsettled on the Web: still in doubt; an unsettled issue; an unsettled state of mind. changeable: subject to change; a changeable climate; the weather is uncertain; unsettled weather with rain and hail and sunshine coming one right after the other. wordnet.princeton.edu/perl/webwn.
Credit and criminal history checks will be conducted on all applicants. For a Top Secret security clearance, the background investigation includes additional record checks which can verify citizenship for the applicant and family members, verification of birth, education, employment history, and military history.
For national security or intelligence jobs in the federal government, you usually need some level of security clearance. Among the highest levels is Top Secret, abbreviated TS. Additional clearances are required for TS-cleared personnel to work on certain highly sensitive programs, known as Special Access Programs.