Work quietly in middle of house (4)
I believe the answer is:
opus
'work' is the definition.
(I've seen this before)
'quietly in middle of house' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'in' is an insertion indicator.
'middle of' indicates the central letters.
The central letters of 'house' are 'ous'.
'p' going within 'ous' is 'OPUS'.
(Other definitions for opus that I've seen before include "Work or composition, usually musical" , "(Numbered) musical composition" , "Composition - magnum __" , "Musical piece" , "Composer's work" .)