Revolutionary piece of journalism's a crass expression of contempt (7)
I believe the answer is:
sarcasm
'contempt' is the definition.
(I've seen this before)
'revolutionary piece of journalism's a crass expression' is the wordplay.
'revolutionary' is a reversal indicator (letters revolve around).
'piece of' indicates the answer is hidden within the clue.
'msacras' can be found hidden inside 'journalisms a crass expression'.
'msacras' back-to-front is 'SARCASM'.
'of' is the link.
(Other definitions for sarcasm that I've seen before include "Satirical and scornful remarks" , "Language expressing scorn or contempt" , "Scornful attitude" , "Scornful jibe" , "The use of irony to mock" .)