Pompey lost the battle of League One's two in-form clubs at Fratton Park.
Kenny Jackett's side controlled much of the play, but did not do enough to test Ben Amos between the sticks.
Jonny Williams opened the scoring for the visitors, who wrapped up a 2-0 victory when substitute Chuks Aneke headed home late on.
Fans can watch the key moments (top video) or register with iFollow to see extended highlihts (middle video) and a full match replay (bottom video).