Journalist caught in disturbance, weakening (9)
I believe the answer is:
reduction
'weakening' is the definition.
(thesaurus)
'journalist caught in disturbance' is the wordplay.
'journalist' becomes 'ed' (short for editor).
'caught in' means one lot of letters goes inside another.
'disturbance' becomes 'ruction' (ruction is a kind of disturbance).
'ed' put inside 'ruction' is 'REDUCTION'.
(Other definitions for reduction that I've seen before include "cut" , "cutback!" , "thickened sauce?" , "from nine to five, for example" , "Introduce (anag) - decrease" .)