Extend green ground outside city (7)
I believe the answer is:
enlarge
'extend' is the definition.
(thesaurus)
'green ground outside city' is the wordplay.
'ground' is an anagram indicator (grind the letters ).
'outside' indicates putting letters inside.
'city' becomes 'la' (Los Angeles).
'green' with letters rearranged gives 'enrge'.
'enrge' enclosing 'la' is 'ENLARGE'.
(Other definitions for enlarge that I've seen before include "Make big" , "Dilate" , "Make bigger in general" , "Make greater" , "swell?" .)