Ferocious fire destroyed church (6)
I believe the answer is:
fierce
'ferocious' is the definition.
(I know that ferocious can be written as fierce)
'fire destroyed church' is the wordplay.
'destroyed' indicates an anagram.
'church' becomes 'CE' (Church of England).
'fire' anagrammed gives 'fier'.
'fier'+'ce'='FIERCE'
(Other definitions for fierce that I've seen before include "Vicious" , "Powerfully aggressive" , "Vehement, furious" , "Extremely violent or intense" , "Unpleasantly extreme, not gentle" .)