In a reading room, it's generally unwelcome (3)
I believe the answer is:
din
'generally unwelcome' is the definition.
I can't tell whether this definition defines the answer.
'in a reading room' is the wordplay.
'in' says the answer is hidden in the clue.
'DIN' is hidden in the letters of 'reading room'.
'it's' is the link.
Can you help me to learn more?
(Other definitions for din that I've seen before include "A lot of noise (3)" , "Clamour" , "Rumpus" , "Cacophony" , "Loud and long noise" .)