Gloomy journalist returning to be dealt with immediately (10)
I believe the answer is:
depressing
'gloomy' is the definition.
(synonyms)
'journalist returning to be dealt with immediately' is the wordplay.
'journalist' becomes 'ed' (short for editor).
'returning' says the letters should be written in reverse.
'to be dealt with immediately' becomes 'pressing' (pressing can mean urgent).
'ed' in reverse letter order is 'de'.
'de'+'pressing'='DEPRESSING'
(Other definitions for depressing that I've seen before include "Making miserable" , "Disheartening" , "Causing dejection" .)