use labelSeparator : "" config of combobox to fix the issue.
Refer below example
Ext.create('Ext.form.ComboBox', {
fieldLabel: 'Choose State',
store: states,
queryMode: 'local',
displayField: 'name',
valueField: 'abbr',
labelSeparator : "",
renderTo: Ext.getBody()
});
Thanks, sure it will work.