Hi, Tarzan-san.
The LATCH pin is a positive edge sensitive pin so connecting this to GND will make it impossible to send instructions, read, or write to the part. As for the CLEAR pin, if it is not going to be used, you may connect this to GND as this is an active high input.
For more details, please refer to the Pin Function Descriptions on page 12 and 13 of the Rev. J of the AD5422 data sheet.
Regards,
Mark