The phrase "good clue" means a helpful hint or piece of information that can lead you to find something or understand a situation better. Full definition
«These mice may give us much better clues as to how these drugs are acting,» he said. (sciencedaily.com)
Designer bags are often worth more than the stuff packed inside, but a $ 700 bag is a pretty good clue there may be pricey items inside too. (travelinsurancereview.net)
The Things also return too, and now the game better clues you in to when to use them. (gametactics.com)