Petty officer upset with media abuse (7)
I believe the answer is:
oppress
'abuse' is the definition.
(I've seen this before)
'petty officer upset with media' is the wordplay.
'petty officer' becomes 'po' (naval abbreviation).
'upset' says the letters should be written backwards.
'with' says to put letters next to each other.
'media' becomes 'press' (the press is part of the media).
'po' in reverse letter order is 'op'.
'op'+'press'='OPPRESS'
(Other definitions for oppress that I've seen before include "Trample down" , "Govern with cruelty and injustice" , "Lie heavy upon" , "Afflict" , "Abuse" .)