Can we translate manndalipakara in Theragatha 863 with “a circular rampart”?
In the Jataka there are many concepts of vastu-purusa-mandala which is a plan for a temple or a city, but this is not expressed with the word mandala/mandalin. The meaning of mandala/mandalin in verses of the Pali canon can be figured through synthesis with “a theory of mandala” in the Arthasastra of Kautilya and “tisu mandalesu” of the Milindapañha.
It means “a unit with peripheral countries led by one great power in the center” and should be treated as the mandala of politics/military affairs.
The mandala comes to mean “the whole unit with order relation in the center and the outskirts” in primitive Buddhism. And when it is located in the latter half of a compound, it means “a thing in the center (or the best thing) among the aggregation of the kind”.
On the other hand, mandalin means “ruler of a (minor) region” used in “a theory of mandala” as explained in the Buddhist Hybrid Sanskrit Dictionary.
Mandalipakara should be translated with “the rampart for (or to protect) a lord or a king of a (minor) region”.