City fails to secure backer (3,7)
I believe the answer is:
los angeles
'city' is the definition.
(Los Angeles is an example)
'fails to secure backer' is the wordplay.
'fails' becomes 'loses' (I've seen this before).
'to secure' means one lot of letters goes inside another (inserted letters are secured inside).
'backer' becomes 'angel' (an angel is a financial backer).
'loses' enclosing 'angel' is 'LOS ANGELES'.
(Other definitions for los angeles that I've seen before include "Second most populous city in the US" , "city abroad" , "Hollywood city" , "centre of population" , "LA, California" .)