A permit to is a document that grants permission to do something. It is usually issued by a government agency or other authority. The term 'permit to' can refer to a variety of documents, such as a driver's license, a hunting license, or a building permit. The three-letter answer to the crossword puzzle is LET, which stands for 'license, exemption, or permit.' A LET is a type of permit that allows an individual or organization to do something that would otherwise be prohibited.