Authentic expression of concern by parliament (3,4,5)
I believe the answer is:
the real thing
'authentic' is the definition.
'expression of concern by parliament' is the wordplay.
'expression of concern' becomes 'there' (as in there, there).
'by' means one lot of letters go next to another.
'parliament' becomes 'althing' (Icelandic parliament).
'there'+'althing'='THE REAL THING'
(Other definitions for the real thing that I've seen before include "genuine" , "Not an imitation or a substitute" .)