Stone to crush — this is just breaking now! (4,5)
I believe the answer is:
stop press
'this is just breaking now' is the definition.
(phrase said when there's breaking news)
'stone to crush' is the wordplay.
'stone' becomes 'st'.
'to crush' becomes 'oppress' ('oppress' can be a synonym of 'crush').
'st'+'oppress'='STOP-PRESS'
(Other definitions for stop press that I've seen before include "Late breaking news" , "newspaper feature" , "Hold the front page!" , "Late news item" , "breaking intelligence" .)