Relative peace, finally, in French city (5)
I believe the answer is:
niece
'relative' is the definition.
(type of relative)
'peace finally in french city' is the wordplay.
'finally' indicates one should take the final letters.
'in' indicates putting letters inside.
'french city' becomes 'nice' (Nice is a French city).
The last letter of 'peace' is 'e'.
'e' put inside 'nice' is 'NIECE'.
(Other definitions for niece that I've seen before include "Young female relative" , "Kinswoman" , "Criminal" , "member of different generation" , "A sibling's child" .)