Gloomy bachelor in northern town (5)
I believe the answer is:
sable
'gloomy' is the definition.
(thesaurus)
'bachelor in northern town' is the wordplay.
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'in' is an insertion indicator.
'northern town' becomes 'sale' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'b' put within 'sale' is 'SABLE'.
Can you help me to learn more?
(Other definitions for sable that I've seen before include "Bales of valuable Russian fur" , "Dark brown fur of the marten" , "Black (heraldry); fur" , "Bales (anag.)" , "Marten's fur - dark black" .)