ignition key

(figuratively) a way of approaching a work of art, a situation, etc. that is useful for deciphering it, interpreting it, and/or understanding it

ready for use, ready to use, turnkey (ready to use without further assembly or test; supplied in a state that is ready to turn on and operate)

(computing) sortkey

(accounting) distribution key, allocation criterion

Alternative spelling of prendre la clef des champs

(figuratively) to close down (of a business), to close up shop

Alternative form of mettre la clé sous la porte

(derogatory, slang) dog; pooch

plural of clé