Hi,

    I hope its not your custom graph view and you should inherit the view and replace policy_vat field like,

    <record id="your_view_inherit" model="ir.ui.view">

            <field name="name">crm.lead.dashboard.lead</field>

            <field name="model">crm.lead</field>

            <field name="inherit_id" ref="base_module(crm).base_graph_view_id"/>

            <field name="arch" type="xml">

                <field name="policy_vat" position="replace">

                    <field name="policy_vat" invisible="1"/>

                </field>

                                                or

                <field name="policy_vat" position="replace">

                </field>

            </field>

        </record>

Thanks