From what I understand, there were Western-style bars and nightclubs in Karachi and Lahore up until Zulfikar Ali Bhutto had them closed down in 1977. Today some of the five star hotels will have “lounges” with DJs and dance floors at night, but there are no real nightclubs.
The closest thing now are the private parties and charity balls. I remember going to a charity event on French Beach a couple years ago that was actually rather nice. But unless your friends/relatives in Pakistan are fairly well-connected, you’re not going to get invited to anything worth going to.