Unsociable person (5)
I believe the answer is:
loner
'unsociable person' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for loner that I've seen before include "Person who prefers his own company" , "Hermit" , "One who avoids company" , "Solitary person" , "Unsociable person" .)