Spell of bad luck?

The crossword question requires a four-letter answer that refers to a “spell of bad luck“. The answer to this question is “HEX“. The word “hex” refers to a type of magic or curse that brings bad luck or misfortune to a person or object. The use of the term “spell” in the crossword question is a clever play on words, as it can refer to both a magical incantation and a period of bad luck. Therefore, the answer “HEX” fits the definition of a “spell of bad luck” perfectly.