That should work, for instance as an answer to "Melyik bútor a kedvenced?" (Which piece of furniture is your favourite?)
But a full sentence is much more fun. :)
Az is the demonstrative pronoun "that", and a is the definite article "the". The problem is, when the next word starts with a vowel, a becomes az (like "a" becomes "an" in English in front of vowel sounds). So you sometimes have that apparent doubling.
Even more problematic, in front of certain words, the demonstrative az can be reduced to a. :´)
Particles are weird.