Most of war cry is complete failure (7)
I believe the answer is:
washout
'complete failure' is the definition.
(I've seen this before)
'most of war cry' is the wordplay.
'most of' means to remove the last letter.
'cry' becomes 'shout' (synonyms).
'war' with its final letter removed is 'wa'.
'wa'+'shout'='WASHOUT'
'is' acts as a link.
(Other definitions for washout that I've seen before include "Flush" , "Cancelled event - utter failure" , "A complete failure - rained off? (4-3)" , "A complete failure - too much rain" , "Cancelled test, for example" .)