City financial backer fails to maintain houses (3,7)
I believe the answer is:
los angeles
'city' is the definition.
(Los Angeles is an example)
'financial backer fails to maintain houses' is the wordplay.
'financial backer' becomes 'angel' (I've seen this before).
'fails to maintain' becomes 'loses' ('lose' can be a synonym of 'fail to maintain').
'houses' means one lot of letters goes inside another.
'angel' going into 'loses' is 'LOS ANGELES'.
(Other definitions for los angeles that I've seen before include "Californian city" , "American city" , "city abroad" , "Second most populous city in the US" , "US city; Victoria de ---, soprano" .)