Home-in-on Definition

verb

(military, of an aircraft) To draw close to a destination, especially using radar; (of a guided missile) to move towards a target.

Wiktionary

(idiomatic) To focus or narrow down to something; to find, draw closer or move towards, as by trial and error or a gradual seeking process.

He used the clues to home in on the source of the flames.
We are homing in on a solution.
Wiktionary