The antonyms for the phrase "clinch the deal" are phrases and terms that express the opposite of finalizing or securing a deal. Some examples include "lose out," "miss the mark," "fail to land the contract," "blow the negotiations," "drop the ball," and "fall through." These phrases imply that even after successful negotiations and discussions, one is not able to secure or finalize a deal due to some reason or other. Therefore, it is essential to keep these antonyms in mind while negotiating deals to avoid any mishaps or disappointments. One can also develop strategies to overcome any obstacles to clinching deals and thus reduce the chances of using these antonyms.