締切
しめきり · shimekiri · JLPT N2 · noun
deadline
⏰ 締切 = shut (締) + cut off (切): the deadline shuts and cuts off late work
締 means tighten or shut, and 切 means cut. Together, 締切 is the moment submissions close and late ones are cut off.
切 — 七 (phonetic) + 刀 (knife radical)
切 is a semantic-phonetic compound: 刀 'knife' gives the meaning of cutting, while 七 supplies the sound. The original sense was to slice or cut with a blade. From there it extended figuratively to 'close to' (as in pressed against) and 'urgent/earnest', as in 切实.