The term 'Singer with the Blackhearts' refers to Joan Jett, a four-letter answer in the crossword puzzle. Joan Jett is an American rock singer, songwriter, composer, musician, record producer and occasional actress. She is best known for her work with the band Joan Jett & the Blackhearts, which had a string of hits in the 1980s, including 'I Love Rock 'n' Roll', 'Crimson and Clover', 'Do You Wanna Touch Me', 'Light of Day', 'Love Is All Around' and 'Bad Reputation'.