The trailer for Last Christmas, a romantic comedy from Bridesmaids director Paul Feig, was released today and features old classics from the former Wham! singer.
But Mr Feig has revealed to the BBC that the full six-minutes of a previously unheard song will feature in the film.
He said: “[George Michael] was putting together his new album when he passed [in 2016].
“And one of our tracks is one of those songs, and it’s just an absolutely amazing song that I’m so excited the world is going to get to hear now.”
He said the song was “celebratory” and added: “We were able to play the entire song, which is almost six minutes long, in the film.”
Fans can listen out for the song at the end of the film, and will have to stick around into the credits to hear the rest of it.
The film also stars Crazy Rich Asians actor Henry Golding.
Last Christmas will centre around Kate (played by Clarke), a woman who is thrown out of her flat after accidentally electrocuting her flatmate’s fish, and is scolded for not working hard enough by her boss.
She reveals to Golding, who will play love interest Tom, that she was so ill she nearly died, a moment particularly personal to Clarke.
The Me Before You star has spoken openly about suffering a stroke eight years ago, and having a potentially fatal brain haemorrhage.
Clarke, 32, started SameYou, a charity dedicated to supporting young people and helping them access resources for recovery.
The film was written by Dame Emma Thompson and Bryony Kimmings, based on a story by Dame Emma and her husband Greg Wise.
Dame Emma also plays Kate’s mother in the film.
The film will be out in the UK on 15 November.