Accessing plant, media controlled (9)
I believe the answer is:
repressed
'controlled' is the definition.
'accessing plant media' is the wordplay.
'accessing' indicates putting letters inside (inserted letters gain access).
'plant' becomes 'reed' (reed is a kind of plant).
'media' becomes 'press' (the press is part of the media).
'reed' enclosing 'press' is 'REPRESSED'.
(Other definitions for repressed that I've seen before include "withdrawn" , "Kept under control; put down" , "Kept bottled up" , "Checked" , "deleted recordings sometimes were" .)