ESTOP is a legal term that stands for 'Emergency STOP'. It is a legal order issued by a court or other authority to prevent a particular action from taking place. It is commonly used in cases where a person or organization is attempting to do something that is illegal or unethical. The term BAR, which is the answer to the crossword puzzle, is an abbreviation of the phrase 'Bring Action to Restrain', which is another way of saying 'STOP'.