The file extension CLX marks the standard dictionaries for spell-checking documents. This format is mainly used in various Adobe products. These files contain word lists in a binary format and are usually located under 'Configuration-> Spelling or -> Content-> Dictionaries', depending on the application in the main folder.
Most often resolving problems with opening CLX files is very simple. Just install an appropriate program that supports such files. All of the listed programs support CLX files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of CLX files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate CLX files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Adobe InDesign applications is not on the list, select "Browse" option in order to manually locate the directory where Adobe InDesign has been installed.
Sometimes problems with opening CLX files may not lie with the application itself, but can arise due to other causes, such as: