Left lout in lounge (4)
I believe the answer is:
loaf
'lounge' is the definition.
('loaf' can be a synonym of 'lounge')
'left lout' is the wordplay.
'left' becomes 'l' (common abbreviation).
'lout' becomes 'oaf' ('oaf' can be a synonym of 'lout').
'l'+'oaf'='LOAF'
'in' is the link.
(Other definitions for loaf that I've seen before include "Idle - head" , "Mass of bread" , "Some bread; 10 (slang)" , "Spend time idly; bread" , "Half of one is better than none" .)