Remove Value of dependent field
Try to use any of these modules.


Conditional Fields - This module definitely solve your issue. How to use.



  Conditional Fields allows you to manage sets of dependencies between
  fields. When a field is “dependent”, it will only be available for
  editing and displayed if the state of the “dependee” field matches the
  right condition. When editing a node (or any other entity type that
  supports fields, like users and categories), the dependent fields are
  dynamically modified with the States API.



Dependent Fields



  The Dependent Fields module (formerly AHAH Dependent Fields) allows
  cck based fields to specify another field as a controller field, and
  react to its changes on the form using AHAH/AJAX without the form
  re-loading.



Dynamic dependent fields



  Makes field value or options depend on other field values when editing
  entity.