Relative peace finally found in European city (5)
I believe the answer is:
niece
'relative' is the definition.
(niece is a kind of relative)
'peace finally found in european city' is the wordplay.
'finally' suggests the final letters.
'found in' indicates putting letters inside.
'european city' becomes 'nice' (I am not sure about this - if you are sure you should believe this answer much more).
The last letter of 'peace' is 'e'.
'e' placed inside 'nice' is 'NIECE'.
Can you help me to learn more?
(Other definitions for niece that I've seen before include "Young female relative" , "Family relative" , "Brother's daughter" , "girl further down the line" , "member of different generation" .)