1
general::
Under suspicion, in trouble, or out of favor, as in Ever since his brother was accused of fraud, he's been under a cloud. This metaphoric expression calls up the image of a single black cloud hanging over an individual. [c. 1500]
American Heritage Idioms
2
general::
Phrase(s): under a cloud (of suspicion)
Fig. suspected of something. • Someone stole some money at work, and now everyone is under a cloud of suspicion. • Even the manager is under a cloud.
McGrawhill's American Idioms And Phrasal Verbs