Babar Azam scored a half-century but England remain in control of the third Test after reducing the home side to 204-5 at tea on day one in Karachi.
Pakistan lost two wickets in the second session with Saud Shakeel, 23, and Mohammad Rizwan, 19, going back to the hut.
Shakeel became the debut wicket for spinner Rehan Ahmed, after Pope took a sharp catch at short-leg, meanwhile Rizwan was caught by Stokes while trying to clear the fence on the bowling of Joe Root.
However, skipper Azam remained solid and was unbeaten on 71 runs, with the help of eight fours, at the break.
Abdullah Shafique, 8, was the first to be dismissed after a ball from Leach skid into his knee roll.
Shan Masood, who came into the side in place of the injured Imam-ul-Haq, top-edged a short one from Mark Wood after scoring 30 runs in 37 balls.
Meanwhile, Azhar Ali was caught by Ben Foakes, in another leg-side strangle, after he gloved one from Robinson. The veteran batter scored 45 runs and was sent packing on the stroke of lunch.
Earlier, Pakistan captain Babar Azam won the toss Saturday and chose to bat against England.
England, on their first Test tour to Pakistan since 2005, lead the series 2-0 after winning the first match by 74 runs in Rawalpindi and the second by 26 in Multan.
The tourists made two changes from the last Test, bringing in wicketkeeper Ben Foakes and Rehan Ahmed in place of James Anderson and Will Jacks.
Rehan, at 18 years and 126 days, becomes the youngest player to debut for England, beating Brian Close´s record of 18 years and 149 days set in 1949.
Senior Pakistan batter Azhar Ali, who on Friday announced the Karachi Test would be his last, is one of four changes in the home side.
Shan Masood, Mohammad Wasim Junior and Nauman Ali also come in, while Imam-ul-Haq (injured), Mohammad Nawaz, Zahid Mahmood and Mohammad Ali were left out.
Wasim, 21, is playing his first Test.
Pakistan: Babar Azam (captain), Abdullah Shafique, Azhar Ali, Shan Masood, Saud Shakeel, Mohammad Rizwan, Agha Salman, Faheem Ashraf, Mohammad Wasim Junior, Abrar Ahmed and Nauman Ali.
England: Ben Stokes (captain), Harry Brook, Zak Crawley, Ben Duckett, Ben Foakes, Jack Leach, Ollie Pope, Ollie Robinson, Joe Root, Mark Wood and Rehan Ahmed.