Meaning: This sentence means that if a talented person is lazy, someone with less talent but who has determination and persistence can achieve more.
Choice of Words: Tenacity means determination and persistence. Conquer means to win a fight or competition. Talent means a natural ability to do something well. Nap means to take a short sleep. When you put them together, "Tenacity conquers talent when talent naps" means that determination and persistence can overcome natural talent if the talented person is not working hard.