Peace - Crimea's flourishing with it (9)
I believe the answer is:
armistice
'peace' is the definition.
(armistice is a kind of peace)
'crimea's flourishing with it' is the wordplay.
'flourishing with' indicates anagramming the letters (letters grow or flourish differently).
'crimeas' anagrammed with 'it' can make 'ARMISTICE'.
(Other definitions for armistice that I've seen before include "Suspension of hostilities" , "Fire is prevented by this" , "End of hostilities" , "Truce" , "when shooting stops" .)