Hi, as you have only evening in Hyderabad you can plan to visit Hussain Sagar lake, Golconda or Charminar. After this you can have dinner at famous Paradise hotel.
Hope it helps you.
Most of the monuments close by 5pm, so you can either enjoy them from outside or go for something else. Please avoid the Nampally area road post 6pm as Numaish (exhibition) is in full flow and traffic is at its peak from 5pm till 9pm. If you like architecture then you can visit old city and check out Charminar, Mecca Masjid and Unani Hospital. You will be able to shop pearls, fabrics and other gift/novelties from the surrounding area and also try out the local cuisine (paradise for non veg eaters). You can also check out the Birla Mandir, Hussain Sagar and Necklace road which are all very near to each other and then probably have food near Mehdipatnam or Towlichowki area (Food hub).
Golconda Fort is closed after 5:30pm, you can go to Char Minar and nearby places but they are kinda overcrowded. I would suggest you to go to Hussain Sagar.