Yobbo (4)
'yobbo' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for lout that I've seen before include "disrespectful person" , "Ruffian" , "A coarse ignorant fellow" , "A noisy, badly behaved youth" , "Boor, oaf" .)
(Other definitions for lager lout that I've seen before include "anti-social sort" , "Boozy yob" , "Drinker behaving antisocially" , "menace" , "Aggressive young drunk" .)