鍛える
きたえる · kitaeru · JLPT N1 · verb-ichidan
to train
🔨 鍛 = 金 (metal) + 段 (stages): metal is hammered in stages, and so is training
Smiths beat steel in repeated rounds, and a trainee builds strength the same way, one stage at a time. 金 metal + 段 stages.