Separated garden set to be redeveloped (9)
I believe the answer is:
estranged
'separated' is the definition.
(thesaurus)
'garden set to be redeveloped' is the wordplay.
'to be redeveloped' indicates an anagram.
'garden'+'set'='gardenset'
'gardenset' is an anagram of 'ESTRANGED'.
(Other definitions for estranged that I've seen before include "Cut off" , "A nerd gets (anag) - separated" , "Sad regent (anag) - disaffected" , "no longer friendly" , "Alienated, disaffected" .)