Unsociable (5)
I believe the answer is:
aloof
'unsociable' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aloof that I've seen before include "Withdrawn, supercilious" , "Displaying supercilious reserve" , "Cool, distant" , "Showing detached attitude" , "Snooty" .)