I tried in many ways :

<record model="ir.actions.act_window" id="base.action_partner_form">

<field name="name">Customers-Crop</field>

</record>

<menuitem name="Customers-crop" id="menu_partner_form" parent="base.menu_sales" action="action_partner_form" sequence="1"/> 

it was creating another menuitem down of Customers as Customers-crop . How to invisible or replace the Customers, can any help me??