Block iron for the late news (4,5)
I believe the answer is:
stop press
'the late news' is the definition.
(I've seen this before)
'block iron' is the wordplay.
'block' becomes 'stop' (synonyms).
'iron' becomes 'press' (I've seen this in another clue).
'stop'+'press'='STOP-PRESS'
'for' acts as a link.
(Other definitions for stop press that I've seen before include "Latest news" , "Hold the front page!" , "breaking intelligence" , "newspaper feature" , "Late news item" .)