Exert force; the Fourth Estate (5)
I believe the answer is:
press
I believe this is a double definition.
'exert force' is the first definition.
(I've seen this in another clue)
'the fourth estate' is the second definition.
(term for the press)
(Other definitions for press that I've seen before include "Squeeze - newspapers - push" , "somewhere to keep clothes" , "Urgency" , "Newspapers - use button!" , "Crush; iron" .)