Southern elite? That's a laugh (6)
I believe the answer is:
scream
'that's a laugh' is the definition.
(scream is a kind of laugh)
'southern elite?' is the wordplay.
'southern' becomes 's' (abbreviation).
'elite?' becomes 'cream' (cream is a kind of elite).
's'+'cream'='SCREAM'
(Other definitions for scream that I've seen before include "Indication of terror - how funny!" , "Riot" , "Shout" , "Utter a piercing cry" , "'Sharp, piercing cry (6)'" .)