Field &-& not defined in MC object &

What causes this issue?

The field you entered is not yet specified as a field of the matchcode
object.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Enter the field as a field of the matchcode object. Branch to the
matchcode object maintenance screen and select <LS>Goto ->
Fields</>.

Error message extract from SAP system. Copyright SAP SE.