Feature of sadism always so sad (6)
I believe the answer is:
dismal
'sad' is the definition.
(thesaurus)
'feature of sadism always so' is the wordplay.
'feature of' says the answer is hidden in the clue.
'DISMAL' is hidden within 'sadism always so'.
(Other definitions for dismal that I've seen before include "Wretched" , "'Gloomy, grim (6)'" , "Miserable" , "Dreary, cheerless" , "Gloomy and cheerless" .)