Before you can answer how safe food is, you have to know what it is. So what is food derived from clones and how is it different from "normal" food? It's the same thing! Cloning is actually a form of reproduction, not a form of genetic manipulation. The cloned animal is identical to the original animal. That is the whole point of cloning!
The misunderstanding with this matter is the difference between cloning and traditional views of genetic engineering. Essentially, genetic manipulation (or engineering) is a method of altering the genes, and thus the cells, of an organism to obtain a benefit, such as increased milk production or leaner meat. This has been traditionally done with injections of growth hormones or selective breeding. Cloning is a way of ensuring that the offspring retain the traits of the breed, particularly their mothers.
One way cloning is accomplished is by taking the egg of an animal, which only has half the chromosomes needed, and switching the nucleus with that of a somatic cell, one that has all the chromosomes. The nucleus in the egg is now identical to a fertilized egg. They trigger the egg to divide using nonchemical means (for example, electricity) and the cell is on its way to becoming another animal, much like sexual reproduction does.
The animal that is born from cloning is identical to those born from sexual reproduction, except it is identical to its mother because it obtained all of its chromosomes from her! Many plants have always done this naturally.
So is food from clones safe? Just as safe as food from its mother, which is another question altogether. Recent advances for increased production have raised questions about the safety of ingesting food treated with chemicals, growth hormone, and antibiotics. Genetic engineering has raised questions about what role genes have in the final product and whether anything "new" is actually being ingested with the "old". Though cloning, by definition, can be considered a type of genetic engineering due to the nuclear transfer, there is not genetic manipulation.
Cloning is not an alteration of genes. It is not a change in proteins. It is a way to breed animals and obtain a known result. This is a step up from the selective breeding of the past. It is a way to ensure the food supply, fight starvation, and keep food prices low.
How safe is food in general? That is the question that must actually be answered because the answer is the same for both cloned and "original" food sources. A mother fed growth hormone will be less safe to eat then her clone fed natural grain.