Cloudy jelly is usually due to improper juicing of the fruit. Fruit should be cooked gently rather than boiled. Dripping should happen through a fine mesh jelly bag or layers of cheesecloth. Never squeeze the jelly bag or cheesecloth. High-sugar jelly tends to have a very crystal clear look from the fact that there is more sugar than juice in the jar. The high level of melted sugar in the jelly creates that look. You may be able to obtain very clear low-sugar jelly by straining the properly obtained juice a number of times.