Little room used by students (3)
I believe the answer is:
den
'little room' is the definition.
'den' can be an answer for 'room' (I've seen this in another clue). I am not certain of the 'little' bit.
'used by students' is the wordplay.
'used by' says the answer is hidden in the clue.
'DEN' is hidden within 'students'.
Can you help me to learn more?
(Other definitions for den that I've seen before include "Cave" , "Miserable place" , "Hidden lair of an animal" , "Animals' shelter" , "Lair for animal or study for gent" .)