The actress will be seen performing the song and dance sequence in the thriller Joker.
She told The Times of India: "It wasn't easy at all. The entire thing made me so nervous.The stage was so huge and there were 700 to 800 people on location as the item number in Joker had to be shot in a village set-up.
"It was at [director] Farah Khan's suggestion that I took it up, and on the D-day I asked her, 'You think I can do it?' and she encouraged me by saying, 'You sure will, girl!'
"I also learnt that you are not supposed to be self-conscious of your body when you are doing such a number as you're the girl everyone's going to be dreaming about in those five minutes and you've got to be at your best.
"The most important thing an actress needs to do when she shakes a leg for an item song is to learn how to transform yourself from being an ordinary girl to a glam diva! It was a good learning experience for me."
In December, Singh said she was interested in doing more commercial cinema despite being famous for her independent film roles.
She has previously said that she finds mainstream Bollywood films "challenging".
Watch 'I Want Fakht You' from Joker below: