Room otherwise includes insect (4)
I believe the answer is:
moth
'insect' is the definition.
(moth is a kind of insect)
'room otherwise includes' is the wordplay.
'includes' indicates a hidden word.
'MOTH' is hidden in the letters of 'room otherwise'.
(Other definitions for moth that I've seen before include "Cloth-eating larva" , "Night flier" , "Insect, mainly nocturnal" , "One of 5 [FAIRIES]" , "Shakespearean fairy?" .)