Item for which "This thing blows" would be a positive review

FAN

["Here’s a helpful hint for your crossword clue:\n\n**\"It might keep you cool or cheer loudly at a concert.\"**\n\nThis hint subtly points to both meanings of \"fan\" (the appliance and the enthusiast) without giving away the answer directly. It’s easier than the original clue but still requires the solver to make the connection."]

The clue plays on the double meaning of the word "fan." In one sense, a "fan" is a device that blows air, making the statement "This thing blows" a literal and positive description of its function. In another sense, "fan" is short for "fanatic," someone who is enthusiastic about something, so a positive review from a fan would indeed be high praise. The wordplay hinges on the pun between the literal and figurative meanings of "blows" and "fan," cleverly tying the two together in a humorous and concise way.