Red-eye ingredient

As a detective, I approached the crossword clue ‘Red-eye ingredient‘ with a curious and analytical mind. First, I noted that ‘red-eye’ is a common term for a flight that departs late at night and arrives early in the morning. Knowing this, I wondered if the solution was something related to caffeine, a common aid for staying awake on red-eye flights. I then considered the phrase ‘ingredient‘ and thought about what one might add to a drink to give it a boost. Espresso, a strong coffee variety, immediately came to mind. Not only is it a common additive to coffee drinks, but it is also known for its ability to keep people awake and alert. Putting all of these pieces together, I confidently submitted the answer ‘ESPRESSO‘ and was thrilled to see it fit perfectly into the crossword grid. This thought process, combined with my knowledge of common travel terminology and caffeine sources, ultimately led me to solve this mystery.