Sharp about-turn's key for peace (5)
I believe the answer is:
truce
'for peace' is the definition.
(truce is a kind of peace)
'sharp about-turn's key' is the wordplay.
'sharp' becomes 'curt' (I've seen this in another clue).
'about' says the letters should be written in reverse.
'turn's key' becomes 'e' (I can't justify this - if you can you should believe this answer much more).
'curt' reversed gives 'truc'.
'truc'+'e'='TRUCE'
Can you help me to learn more?
(Other definitions for truce that I've seen before include "Temporary ceasefire" , "peace initiative" , "Agreed break in hostilities" , "Agreement to stop battle" , "Agreement to suspend fighting" .)