House knocked over in Mumbai -- messy! (4)
I believe the answer is:
semi
'house' is the definition.
(I've seen this before)
'knocked over in mumbai messy' is the wordplay.
'knocked over' says the letters should be written backwards.
'in' indicates the answer is hidden within the clue.
'imes' is hidden in the letters of 'mumbai messy'.
'imes' written backwards gives 'SEMI'.
(Other definitions for semi that I've seen before include "Not quite the biggest tie" , "Half (pfx)" , "The last but one round" , "Prefix meaning half or partly" , "Style of house" .)