Independent exterior (7)
I believe the answer is:
outside
This clue is a double definition.
'independent' is the first definition.
(thesaurus)
'exterior' is the second definition.
(I know that exterior can be written as outside)
(Other definitions for outside that I've seen before include "External surface" , "Alfresco" , "Al fresco" , "having emerged from the tunnel?" , "Unlikely" .)