Hi Ankita,
Invalidate method is used to invalidate/Clear all elements of a node.
You can use the method as below:
DATA lo_nd_cn_input TYPE REF TO if_wd_context_node.
lo_nd_cn_input = wd_context->get_child_node( name = wd_this->wdctx_cn_input ),
lo_nd_cn_input->invalidate( ).
Regards,
Sanjeev Kotwal.