Study old city that's a bit gloomy (4)
I believe the answer is:
dour
'gloomy' is the definition.
(I've seen this in another clue)
'study old city' is the wordplay.
'study' becomes 'do' (to 'do' a subject at university is to study it).
'old city' becomes 'ur' (ancient Sumerian city state).
'do'+'ur'='DOUR'
'that's a bit' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for dour that I've seen before include "Sullen - hard - obstinate" , "Severe, gloomy-looking" , "'Sullen, sour (4)'" , "Grim and gloomy-looking" , "Determined - grim" .)