This wall may not be unusual except that it's badly collapsed and.... straight. Straight walls tend to be post-Clearance, 1830 onwards, and most of these are still in fairly good condition. So this one is a little different.
Looking at a Bing satellite image of the area is fascinating. '1' is the point where the photograph was taken, looking roughly northwest. The wall continues across the landscape for a mile or so, reaching almost as far as the Allt Choiremhuilinn with only a couple of slight bends. Compare it with the wall marked '2-2-2', which waggles all over the place. '1' is also clearly younger than '2', as it cuts across it where they meet.
'2-2-2' is what is called a 'head dyke', the main wall that ran round the outer perimeter of a clachan's arable land. The clachan in this case is Choiremhuilinn. '3' is obviously an even older wall than both '1' and '2' as it has decayed to the point where, on the ground, it's not easily visible.
That this is good arable land is evident from the many fields of lazy beds, particularly in the western part of this image.
The straight wall '1', which cuts right across the clachan's fields and walls, isn't shown extending beyond '2' - but it probably did, but was neglected when Bald drew his made.
This leaves us with some questions. What was the purpose of this unusual, old, straight wall, and what is its age? I'll take a guess at its age. I wonder if Sir Alexander Murray of Stanhope, who had the Ardnamurchan Estate in the early18th century and was responsible for the very straight drainage ditches that he had dug to drain the hills, had any thing to do with it.