The context is the Anglo-Pashto Wars, and I am guessing Lear is writing during or probably more likely in the lead up to the Second Anglo-Pashto War (1878-1880) also known as the Second Anglo-Pashto War.

Swat is the Swat Valley in modern Afghanistan. This was the center of Pashto (also called Pashtun and particularly in historical sources Pathan) culture, and by the time of the Akond (or Akhund) of Swat, a large Pashto state. The Akhund of Swat, also known as Saidu Baba, was an important religious leader in an area where religious leaders were particularly important. For the last several decades of his life, he wielded both religious and political control.

Notice that this is the lead up to the Second Anglo-Pashto War. The First was the Anglo-Afghan War of 1839-1842 (there was a third one in 1919). The outcomes of these wars aren't particularly important for understanding Lear, but why there were wars in the first place is: these conflicts were all part of the so-called "Great Game" (wiki) between the UK and Russia.

The important thing to realize is that the 19th century is a time of rapidly expanding Empire. Empire seemed to make wealth, to make countries great. Countries without empires wanted "their place in the sun" and countries with Empires sought to consolidate, expand, and extract more wealth from their imperial holdings. Russia had a primarily contiguous empire that gradually, and by the 19th century it was expanding mostly East and South. This wiki article has some good maps. Britain, meanwhile, was well aware that its most profitable colony was India and sought to consolidate its rule their. This two and a half minute youtube video shows the colonial holdings in India over time. If you skip straight to 1:30, you won't miss anything important. Pay special attention to the Northwest frontier in the 19th century, because that's what this is. It's also worth noting that Sikhs had been moving northwest into Afghanistan even before they were conquered by the British.

The point is, Russia's southward expansion into Central Asia and the UK's northward expansion from India were on a (very slow) collision course. Notice, too, that a lot of this is about indirect rule. In fact, that's what both Anglo-Pashto/Anglo-Afghan wars were about. After the 1763 Treaty of Paris (ending the Seven Years War, known in America as the French and Indian War), the French all but abandoned the Indian subcontinent leaving it open to British colonization. As you can see from the video above, Britain did that (a good deal of it, really up until Independence even, was indirect rule). The British began showing interest in Afghanistan as early as 1809 when they signed a treaty with the Durrani Emir of Afghanistan. They did so specifically because they were already worried about expanding Russian influence, and basically that's what it continue to be for the next century. Afghanistan, mind you, wasn't the only front of the Great Game--there was also Tibet and Iran and others--but it was the most consistent in many ways. But just like I know names like Fallujah and The Sanh because the American military had major engagements name, and Pyongyang is in the news right now, a British subject in the 19th century would have a vague sense of what's going on in Afghanistan, where after the Emir of Afghanistan himself, one of the most important local players was a man known as the Akhund of Swat. Perhaps something equivalent today would the Rohingya or Darfur or Kony (2012)--they're names that many have heard of, but fewer could point to where they are on a map.