It is possible to create a cross-reference in any field of the "Text" type. No special layout is needed.
I'm quoting from MultiTerm 2011 online help. The information give there is a bit unclear in some points.
Before you begin:
• Carry out a search to find the entry that requires a cross-reference. Click on the relevant term in the Hit List to open the corresponding entry in the entry pane.
• Choose a layout that includes distinctive formatting for cross-reference text. This will make your cross-references clearly visible in the entry pane. See About Layouts.
You can neglect the bit about selecting a layout unless you've created your own layout. All built-in MultiTerm layouts display cross-references as blue text with underline.
1. Select Edit > Edit from the menu or right-click on the term and select Edit.
MultiTerm switches to edit mode. The entry structure reflects the termbase definition or those parts of it that are available according to the settings defined in the currently selected layout or input model.
2. Select the text for which you want to create a cross-reference. The cross-reference text must belong to a text field, and the editing box must remain closed as you select the text.
Cross-references are only available in fields of the "Text" type. You cannot create a cross-reference in term fields, in picklists, number or date fields.
3. Right-click to open the Manage a Cross-reference dialog.
Select the type of cross-reference you want from the choices on the left-hand side of the dialog:
More precisely, right-click the selected text to open the cross-reference dialog.
[Edited at 2013-03-15 15:13 GMT]