On drugs, southern English getting old-fashioned (7)
I believe the answer is:
sedated
'on drugs' is the definition.
'southern english getting old-fashioned' is the wordplay.
'southern' becomes 's' (abbreviation).
'english' becomes 'e' (abbreviation).
'getting' is a charade indicator (letters next to each other).
'old fashioned' becomes 'dated' (I've seen this before).
's'+'e'+'dated'='SEDATED'
(Other definitions for sedated that I've seen before include "kept calm" , "Calmed with drugs" , "Dead set (anag) - tranquillised" , "Tranquillized" , "Tranquilised" .)