Clandestine: kept secret or done secretively, especially because illicit.
Illicit: forbidden by law, rules, or custom.
Sextortion: As used to describe an abuse of power, sextortion is a form of corruption in which people entrusted with power – such as government officials, judges, educators, law enforcement personnel, and employers – seek to extort sexual favors in exchange for something within their authority to grant or withhold. Examples of such abuses of power include: government officials who request sexual favors to obtain licenses or permits, teachers who trade good grades for sex with students, and employers who make providing sexual favors a condition of obtaining a job.