Peace offering? (5)
'peace offering' is the definition.
(synonyms)
This is all the clue.
(Other definitions for olive branch that I've seen before include "One offered in peace" , "Offer of reconciliation" , "that stands for peace" , "offered to cool things?" , "Emblem of peace" .)
(Other definitions for nobel that I've seen before include "6 24 113 [SCAN-DIN-AVIAN] chemist" , "Dynamite inventor, Prize founder" , "Swedish prize-giver" , "Founder of many prizes" , "Prize title" .)