Old Danish city relies on trade (8)
I believe the answer is:
elsinore
'old danish city' is the definition.
'elsinore' can be an answer for 'city' (I have seen 'Danish city' mean 'elsinore' so perhaps 'city' could also mean 'elsinore'). I'm not certain of the 'old danish' bit.
'relies on trade' is the wordplay.
'relies on' anagrams to 'ELSINORE'.
But, I am not sure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for elsinore that I've seen before include "Scene of Hamlet" , "haunted castle?" , "Tragic scene" , "Danish port, setting of Shakespeare's Hamlet" , "Hamlet's home" .)