Journo back before second public meeting (4)
I believe the answer is:
demo
'public meeting' is the definition.
(short for demonstration - public protest)
'journo back before second' is the wordplay.
'journo' becomes 'ed' (I've seen this in other clues).
'back' shows that the letters should be reversed in order.
'before' is a charade indicator (letters next to each other).
'second' becomes 'mo' (both are short periods of time).
'ed' backwards is 'de'.
'de'+'mo'='DEMO'
(Other definitions for demo that I've seen before include "illustration" , "Public protest meeting" , "Protest (abbr)" , "Political protest" , "March (abbr)" .)