Buried: end terrible in ancient city (5)
I believe the answer is:
under
'buried' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I don't see?
'end terrible in ancient city' is the wordplay.
'terrible' is an anagram indicator.
'in' is an insertion indicator.
'ancient city' becomes 'ur'.
'end' is an anagram of 'nde'.
'nde' inserted inside 'ur' is 'UNDER'.
Can you help me to learn more?
(Other definitions for under that I've seen before include "See 16 Down" , "Dylan Thomas wrote '. . . . . Milk Wood'" , "Being short" , "In a state of unconsciousness" , "Beneath or subordinate to" .)