Hi Anirban,
You can try with below code on button click.
data: lr_cuco type ref to cl_crmcmp_I_cucohiddenvie_impl.
lr_cuco ?= get_custom_controller( 'GLOBAL.CRMCMP_IC_FRAME/CuCoHiddenView' ).
clear lr_cuco->scratchpad_text.
Hope this will be useful.
Regards,
Naresh