Row initiated by father on edge (8)
I believe the answer is:
Here is my best explanation:
'edge' is the definition.
(frontier is a kind of edge)
'row initiated by father on' is the subsidiary indication.
'row' becomes 'tier' (tier is a kind of row**).
'initiated by' says to put letters next to each other (some letters go at the start of others).
'father' becomes 'fr'.
'tier' after 'fron' is 'frontier'.
(Other definitions for frontier that I've seen before include "Limit", "Border of country", "Land-border of a country", "Wilderness at the edge of a settled area", "Border separating two countries", "International boundary", "Boundary, border", "Verge", "Land border of a country" and "National border".)