Untidy fringe in which there's nothing alien (7)
I believe the answer is:
foreign
'alien' is the definition.
(I know that alien can be written as foreign)
'untidy fringe in which there's nothing' is the wordplay.
'untidy' is an anagram indicator.
'in which' is an insertion indicator.
'there's nothing' becomes 'o' (I've seen this in other clues).
'fringe' anagrammed gives 'freign'.
'freign' placed around 'o' is 'FOREIGN'.
(Other definitions for foreign that I've seen before include "Not native - maybe of Niger" , "Non-native" , "not appropriate" , "Of or from another country" , "not typical" .)