Though Delhi is not sufficient for one day. But still you can visit Mehrauli Archaeological Park (the hidden gem). Akshar dham and Bangla Sahib Gurudwara are also there. and if you have 2 or 3 days in your hand go to Agra Fatehpur Sikri. Must visit place.
You can also visit Qutub minar as it is near Archeological park. After visit these two, book a uber and visit India gate and Bangla Sahib Gurudwara. One day is easily covered.
Have a look at these places. I think, it is helpful.
Akshardham Temple / Swaminarayan Temple
Humayun's Tomb
Raj Ghat
Red Fort
Birla Mandir / Laksminarayan Temple