Unfortunately preys on Flemish city (5)
I believe the answer is:
ypres
'flemish city' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'unfortunately preys' is the wordplay.
'unfortunately' indicates an anagram (a bad or unfortunate spelling).
'preys' anagrammed gives 'YPRES'.
'on' is the link.
Can you help me to learn more?
(Other definitions for ypres that I've seen before include "WW1 battle location" , "WW1 battle site" , "Scene of action" , "in northern Europe" , "WWI battle site" .)