Something declared fresh needs sending back (3)
I believe the answer is:
'something declared' is the definition.
(as in declaring war)
'fresh needs sending back' is the wordplay.
'fresh' becomes 'raw' (I've seen this in another clue).
'needs sending back' shows that the letters should be reversed in order.
'raw' in reverse letter order is 'WAR'.
(Other definitions for war that I've seen before include "Battle" , "Hostile situation" , "State of armed conflict" , "Sustained conflict" , "Combat" .)