Translation:Un fin de semana.
Spanish and English do not have perfectly equivilant words, and so when they have a phrase that means the same as our words, we have to Translate it. I know when you are learning a language you don't expect to have to Translate, but Alas that is the only option.
On another note, you can say "A" or "An" before the phrase "End of week" but you can do the same with the word "Weekend" proving your logic is a little off.
I wish you a good day.