hone 
/ˈhoʊn/ verb
hones; honed; hon·ing /ˈhoʊn/ verb [+ obj] 1 : to sharpen (something, such as a knife) with a stone
▪ hone a blade 2 : to make (something, such as a skill) better or more effective
▪ She honed her language skills by reading and writing every day.
▪ hone a blade
▪ She honed her language skills by reading and writing every day.
hone in on
[phrasal verb] US : to find and go directly toward (someone or something)
▪ The missile was honing in on [=homing in on] its target. — usually used figuratively ▪ Researchers are honing in on the cause of the disease. ◊Although hone in on is widely used, many people regard it as an error for home in on.
▪ The missile was honing in on [=homing in on] its target. — usually used figuratively ▪ Researchers are honing in on the cause of the disease. ◊Although hone in on is widely used, many people regard it as an error for home in on.
