hello you can try this

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

<field name="name">timesheet.form.readonly manager</field>

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

<field name="inherit_id" ref="view_ref"/>

<field name="groups_id" eval="[(6, 0, [ref('group_res_manager')])]"/>

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

<field name="employee_id" position="attributes">

<attribute name="readonly" >1</attribute>

</field>

</field>

</record>