The term 'Royal Domain in Actual Miles' can be solved by the crossword solution 'REALM' which is a five letter word. A REALM is an area of land that is ruled by a monarch, such as a kingdom or empire. The term 'actual miles' refers to the physical size of the land, as opposed to the political boundaries of the REALM. Therefore, the term 'Royal Domain in Actual Miles' refers to the physical size of a monarchy's land.