My tooth is loose, believed caused by clenching jaw at night. I wear a retainer at night. Any solutions, advice?

Occlusal Trauma. Traumatic occlusion is mostly treated by a periodontal evaluation and a procedure called occlusal equilibration to achieve balance and proper alignment. See your dentist/orthodontist for eval.
Have it examined. What you think might be the problem and what the actual problem is can be two different things. Best to have your dentist take a look.
Tooth mobility. Can be caused by traumatic occlusion, parafunctional habits, abscess, gum disease, bone loss, fracture, malocclusion, etc. please see your Dentist to determine the cause and to provide the appropriate treatment.