Clean code is code that does what you expect it to do without many surprises. It is simple, not clever. Effortless to follow. Each part handles one idea at a time, at the same abstraction level. Doesn't force you to mentally juggle many balls at the same time.

The code often tells you a story, it communicates how the programmer (author) described the problem, the solutions and the trade-offs. Very similar to writing.

Maybe it is a vague term. But it is not an excuse to write "bad" code. Perhaps every team need to have a "definition of clean code" for themselves.