Redress, to fanatics, is breaking out (12)
I believe the answer is:
satisfaction
'redress' is the definition.
(satisfaction is a kind of redress)
'to fanatics is breaking out' is the wordplay.
'breaking out' is an anagram indicator.
'to'+'fanatics'+'is'='tofanaticsis'
'tofanaticsis' anagrammed gives 'SATISFACTION'.
(Other definitions for satisfaction that I've seen before include "Fulfilment; compensation" , "Gratification" , "I can't get no - (Rolling Stones)" , "Contentment; reparation" , "Pleasure" .)