I have loss of vision in one eye, several times a month. Is it caused by a temporary blockage like a blood clot?

Could be a TIA. A temporary loss of vision in one eye can be a sign of a TIA also known as a transient ischemic attack. It can be caused by small blood clots (emboli) that break off from either the heart or carotid artery in the neck. See your primary care provider for evaluation that may include ultrasound studies.
Significant. Transient vision loss in one eye is a significant visual complaint and requires urgent ophthalmic assessment. As the questioner indicates, a blot clot is a possibility though many other causes are known.