Ferocious fire destroyed empty campsite (6)
I believe the answer is:
fierce
'ferocious' is the definition.
(synonyms)
'fire destroyed empty campsite' is the wordplay.
'destroyed' indicates an anagram.
'empty' suggests removing the centre.
'campsite' with its centre removed is 'ce'.
'fire' anagrammed gives 'fier'.
'fier'+'ce'='FIERCE'
(Other definitions for fierce that I've seen before include "Ruthlessly violent" , "Aggressive; intense" , "Violent in temper or manner" , "Intensely aggressive" , "Violent and aggressive" .)