Work under house band (4)
I believe the answer is:
hoop
'band' is the definition.
(I've seen this before)
'work under house' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'under' means one lot of letters go next to another.
'house' becomes 'ho' (abbreviation for house).
'op' put after 'ho' is 'HOOP'.
(Other definitions for hoop that I've seen before include "Large ring" , "Arch used in croquet" , "round during dance" , "Wood, metal or plastic band" , "Croquet target" .)