Gloomy about group of actors (8)
I believe the answer is:
overcast
'gloomy' is the definition.
(thesaurus)
'about group of actors' is the wordplay.
'about' becomes 'over' (I've seen this before).
'group of actors' becomes 'cast' (I've seen this before).
'over'+'cast'='OVERCAST'
(Other definitions for overcast that I've seen before include "State of a dark cloudy sky" , "not entirely fair" , "Of sky, covered with cloud" , "Not very bright" , "Cloud-covered" .)