Rush concerning journalist (4)
I believe the answer is:
reed
'rush' is the definition.
(I've seen this before)
'concerning journalist' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'journalist' becomes 'ed' (short for editor).
're'+'ed'='REED'
(Other definitions for reed that I've seen before include "piece for organ" , "Marsh plant with tall straight stem" , "Rush" , "A blade of march grass" , "Stalk" .)