Prevent anger onslaught (7)
I believe the answer is:
barrage
'onslaught' is the definition.
(I know that onslaught can be written as barrage)
'prevent anger' is the wordplay.
'prevent' becomes 'bar' (I've seen this in another clue).
'anger' becomes 'rage' (rage is a kind of anger).
'bar'+'rage'='BARRAGE'
(Other definitions for barrage that I've seen before include "Sustained fire" , "Artificial obstruction in a river" , "Prolonged artillery fire" , "prolonged attack" , "Continuous artillery fire" .)