Gloomy feature lacking moisture outside (6)
I believe the answer is:
dreary
'gloomy' is the definition.
(thesaurus)
'feature lacking moisture outside' is the wordplay.
'feature' becomes 'ear' (I've seen this in other clues).
'lacking moisture' becomes 'dry' (I've seen this before).
'outside' means one lot of letters goes inside another.
'ear' placed into 'dry' is 'DREARY'.
(Other definitions for dreary that I've seen before include "Dull and depressing" , "routine" , "Grey and dull" , "avoiding exciting stuff" , "Cheerless and dull" .)