The phrase "big clue" means a piece of information or evidence that is important and can help solve a puzzle or mystery.
Sentences with «big clue»
That was one of my first big clues as to the effect of inflammatory foods in my body. (whatsupforkids.com)
Your dating photos should be giving people big clues about what you're like as a person. (uk.match.com)
Based on gathered intelligence, themes from previous product cycles and one big clue in the pictures, we could have the entry - level flagship in our sights. (pocketnow.com)