It's to be discouraged in the reading room (3)

I believe the answer is:

din

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

'it's to be discouraged' is the definition.
I can't tell whether this definition defines the answer.

'in the reading room' is the wordplay.
'in' says the answer is hidden in the clue.
'DIN' can be found hidden inside 'reading room'.

Can you help me to learn more?

(Other definitions for din that I've seen before include "Hubbub" , "'Continuous, unpleasant noise (3)'" , "Too much noise" , "Rumpus" , "Loud annoying noise" .)

I've seen this clue in the Evening Standard.

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