The press (6,6)
'the press' is the definition.
(synonyms)
This is all the clue.
(Other definitions for fourth estate that I've seen before include "addition to three-car family?" , "Journalistic profession - press" .)
'the press' is the definition.
(the press is part of the media)
This is all the clue.
(Other definitions for media that I've seen before include "journalists' outlets" , "Reporters" , "sources of information" , "the box etc" , "Eg, newspapers, TV" .)