The term 'A Hard Day's Write Subject' is a reference to the Beatles, a British rock band that formed in 1960 and became one of the most successful and influential acts in music history. The band consisted of John Lennon, Paul McCartney, George Harrison, and Ringo Starr. The phrase 'A Hard Day's Write' is a play on words of the title of their 1964 film 'A Hard Day's Night'. The subject of the crossword solutions is thus the Beatles.