put someone on the spot idiom
C2 让（某人）难堪;使（某人）为难
If you put someone on the spot, you cause them embarrassment or difficulty by forcing them at that moment to answer a difficult question or make an important decision.
Mira rather put the boss on the spot by asking him when he was going to give us a pay rise. 米拉问老板打算什么时候给我们加薪，可真让他当场下不了台。