The CLEAR field-list and CLEAR SCREEN ARRAY screen-array.* instructions clear the value buffer of specified form fields. The buffers are directly changed in the current form, and the program variables bound to the dialog are left unchanged. CLEAR can be used outside any dialog instruction, such as the DISPLAY BY NAME / TO instructions.
When a dialog is configured with the UNBUFFERED mode, there is no reason to clear field buffers since any variable assignment will synchronize field buffers. Actually, changing the field buffers with DISPLAY or CLEAR instruction in an UNBUFFERED dialog will have no visual effect, because the variables bound to the dialog will be used to reset the field buffer just before giving control back to the user. To clear fields of an UNBUFEFERED dialog, just set to NULL the variables bound to the dialog. However, when using a CONSTRUCT, no program variables are associated to the dialog and no UNBUFFERED concept exits, and the CLEAR or DISPLAY TO / BY NAME instructions are the only way to modify the CONSTRUCT fields.
A screen array with a screen-line specification doesn't make much sense in a GUI application using TABLE containers, you can therefore use the CLEAR SCREEN ARRAY instruction to clear all rows of a list.