White/clear vaginal discharge no blood. Just had normal vag u/s.last pap cotest 5 yrs ago normal. Am postmenopausal. Could it be cancer?

See your doctor. Postmenopausal vaginal discharge can be caused by many things including infections (yeast or bacterial) or occasionally worrisome things such as cancer. Your family doctor or gynecologist can determine the cause and I recommend that you make an appointment for an examination.