Robin's green city (7)
I believe the answer is:
lincoln
This might be a double definition.
'robin's green' is the first definition.
'lincoln' can be an answer for 'green' (Lincoln green is a shade of green). I am not sure about the 'robin's' bit.
'city' is the second definition.
(Lincoln is an English city)
(Other definitions for lincoln that I've seen before include "US politician?" , "An assassinated US president" , "Capital city of Nebraska" , "US president who gave Gettysburg Address" , "US car marque" .)