do在此为不及物动词，意为  be enough, be adequate. 足够了，行，可以。

《韦氏高阶》do

 to be enough : to be adequate

[no object]

• I don't need any more cake, thank you. One piece will do. [=one piece is enough]

• I'd prefer to use glue, but tape will/would do.

The speech had its fine point, but it just wouldn't do. 这个演讲有其亮点，但还远不够。