Wiktionary
n. An ordered sequence of named people who would succeed to a particular office upon the death, resignation or removal of the current occupant; constructed using the rules of an established order of succession.
WordNet
n. the order in which individuals are expected to succeed one another in some official position
Usage examples of "line of succession".
In our diagram the line of succession is broken at regular intervals by small numbered letters marking the successive forms which have become sufficiently distinct to be recorded as varieties.
An heir presumptive in direct line of succession to the clan chieftainship staffed a yacht or a plane.
By law Sansa is next in line of succession, so Winterfell and the north would pass to her.
Sooner or later the boy had to accept the fact that he was in close line of succession to the throne of the Holy Roman Empire, the largest and most powerful realm in Christendom.
Richard and I were never in the line of succession, but Richard liked to pretend to have royal blood.