签下 + 了 + Object
The verb 签下 (qiānxià) means "to sign" in the sense of finalizing a contract, deal, or agreement. The directional complement 下 adds a sense of completion and commitment, distinguishing it from the more general 签. It is commonly used in business and sports contexts.
球队刚刚签下了一位外籍球员。
Qiúduì gānggāng qiān xià le yī wèi wàijí qiúyuán.
The team just signed a foreign player.
我们公司昨天签下了一笔大订单。
Wǒmen gōngsī zuótiān qiān xià le yī bǐ dà dìngdān.
Our company signed a big order yesterday.
她终于签下了人生中第一份工作合同。
Tā zhōngyú qiān xià le rénshēng zhōng dì yī fèn gōngzuò hétong.
She finally signed the first employment contract of her life.