Full version: "Under a cloud of suspicion." Someone under a cloud is someone who is suspected of wrongdoing without clear evidence of guilt. Ex.: "As rumors of a plea deal emerge, Representative Charles Rangel remains under a cloud of suspicion of ethics violations despite denying all wrongdoing." (This is a real case happening right now.) Despite denials, allegations that have not been proven in a trial (a trial which may never occur of a plea deal happens) have clouded Rep. Rangel's reputation.