Excellent female with big back comes to city (5)
I believe the answer is:
sofia
'to city' is the definition.
(Sofia is an example)
'excellent female with big back' is the wordplay.
'excellent' becomes 'ai' (resembles 'A1', old-fashioned term for excellent).
'female' becomes 'f' (abbreviation).
'with' is a charade indicator (letters next to each other).
'big' becomes 'os' (abbreviation for oversize).
'back' says the letters should be written in reverse.
'ai'+'f'+'os'='aifos'
'aifos' reversed gives 'SOFIA'.
'comes' acts as a link.
(Other definitions for sofia that I've seen before include "capital place" , "capital city" , "Capital of Bulgaria" , "Balkan capital" , "Bulgarian capital" .)