Extend green plan around city (7)
I believe the answer is:
enlarge
'extend' is the definition.
(thesaurus)
'green plan around city' is the wordplay.
'plan' indicates an anagram (plan can mean organise).
'around' is an insertion indicator.
'city' becomes 'la' (Los Angeles).
'green' with letters rearranged gives 'enrge'.
'enrge' going around 'la' is 'ENLARGE'.
(Other definitions for enlarge that I've seen before include "Widen" , "Blow up" , "Describe in more detail" , "General (anag)" , "Make greater" .)