The ability to clear our linked fields already exists using an on-screen business rule. The missing component, to unlink the contract record, can be satisfied by voting on this idea instead (a more generic feature request): New Business Rule Action: Unlink Existing Record
There should be a way to clear/reset a section of data (especially the contact area). In FP11 we were able to clear the contact data with one click and provide new information. I would like to see this functionality in FP12.