Outer ____ (5)
'outer' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for exterior that I've seen before include "Foreign" , "Facade" , "covering" , "Outside" , "Outdoor" .)
'outer' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for external that I've seen before include "Lying outside" , "Superficial" , "Outward" , "involving foreign nations" , "Outer" .)
(Other definitions for space that I've seen before include ""The final frontier"" , "Interstellar vacuum" , "Free area" , "Unfilled region" , "Room; gap" .)