The reason a user may see such entries in the operating system’s process table, is simply because the parent process has not read the status of the process. Orphaned defunct processes are eventually inherited by the system init process and will be removed eventually.

How do I clean up the defunct process in Linux?

The only way to get rid of defunct processes that is certain is to reboot the box. Another way that SOMETIMES gets rid of defunct processes is to do a kill of the PPID. In your case that would be PID 7755.

How do you stop a defunct process?

The only way you could remove the zombie/defunct process, would be to kill the parent. Since the parent is init (pid 1), that would also take down your system.