Unprepared for war breaking out (3)
I believe the answer is:
raw
'unprepared' is the definition.
(I've seen this in another clue)
'war breaking out' is the wordplay.
'breaking out' indicates an anagram.
'war' with letters rearranged gives 'RAW'.
'for' acts as a link.
(Other definitions for raw that I've seen before include "Not prepared" , "Uncooked; immature" , "Abraded" , "not manufactured" , "Uncooked or unsavoury" .)