Isolated devastated ruins outside Los Angeles (7)
I believe the answer is:
insular
'isolated' is the definition.
(thesaurus)
'devastated ruins outside los angeles' is the wordplay.
'devastated' indicates an anagram (devastate literally means destroy or lay waste to).
'outside' means one lot of letters goes inside another.
'los angeles' becomes 'la'.
'ruins' is an anagram of 'insur'.
'insur' placed around 'la' is 'INSULAR'.
(Other definitions for insular that I've seen before include "Lacking contact with others" , "Inward-looking" , "Circumscribed" , "Run sail (anag.)" , "Detached - urinals (anag)" .)