expression, godan verb (-gu)
sharpen one's claws
Literal meaning of a cat or other animal sharpening its claws; also used figuratively for someone honing their skills or preparing for an attack.
猫が柱で爪を研いでいる。
The cat is sharpening its claws on the post.
彼はライバルに勝つために、密かに爪を研いでいた
He was secretly sharpening his skills to beat his rival.