Something poetic, for instance, in a cathedral city (5)
I believe the answer is:
elegy
'something poetic' is the definition.
I can't judge whether this definition defines the answer.
'for instance in a cathedral city' is the wordplay.
'for instance' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'in' is an insertion indicator.
'a cathedral city' becomes 'Ely' (English city with a cathedral).
'eg' going inside 'ely' is 'ELEGY'.
Can you help me to learn more?
(Other definitions for elegy that I've seen before include "Work of poet" , "Sad work" , "Plaintive poem" , "Song of lament" , "Sorrowful poem/song" .)