Nonsense, but it keeps some boys quiet! (4)

I believe the answer is:

bosh

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

This clue could be a double definition.

'nonsense' is the first definition.
(bosh is a kind of nonsense)

'it keeps some boys quiet' is the second definition.
The definition suggests a singular noun which matches the answer.

'but' acts as a link.

Can you help me to learn more?

(Other definitions for bosh that I've seen before include "Twaddle" , "Nonsense!" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app