up a tree
In a difficult situation, as in They found the drugs in his suitcase, so he was up a tree. This expression alludes to an animal, such as a raccoon or squirrel, that climbs a tree for refuge from attackers, which then surround the tree so it cannot come down. [Colloquial; early 1800s]
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.