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.
This is hierarchically the first security clearance to get, typically requiring a few weeks to a few months of investigation. A Confidential clearance requires a NACLC investigation which dates back 7 years on the subject's record and must be renewed (with another investigation) every 15 years.