Yob left, excluded (4)
I believe the answer is:
lout
'yob' is the definition.
(both can mean an antisocial young man)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for lout that I've seen before include "Boor, roughneck" , "Yahoo" , "Lob" , "Boor, oaf" , "Ill-mannered or aggressive man" .)