Crossword Genius

It doesn't become a grown-up (12)

Ross

I believe the answer is:

childishness

I'm a little stuck... Click here to teach me more about this clue!

'it doesn't become a grown-up' is the definition.
The definition suggests a singular noun which matches the answer.

This is all the clue.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.