Relative peace finally in part of France (5)
I believe the answer is:
'relative' is the definition.
(type of relative)
'peace finally in part of france' is the wordplay.
'finally' says to take the final letters.
'in' is an insertion indicator.
'part of france' becomes 'nice' (Nice is a French city).
The final letter of 'peace' is 'e'.
'e' inserted into 'nice' is 'NIECE'.
(Other definitions for niece that I've seen before include "Female relation" , "Brother's girl" , "member of different generation" , "A sibling's child" , "Preparation for curdling milk" .)