Grave wrecked in utter barbarity (8)
I believe the answer is:
savagery
'barbarity' is the definition.
(synonyms)
'grave wrecked in utter' is the wordplay.
'wrecked' indicates an anagram.
'in' is an insertion indicator.
'utter' becomes 'say' (to utter something is to speak or say it).
'grave' with letters rearranged gives 'vager'.
'vager' going into 'say' is 'SAVAGERY'.
(Other definitions for savagery that I've seen before include "Barbarism, brutality" , "Vicious cruelty" , "barbarous attack?" , "Barbarous cruelty" , "Ferocity or uncivilised condition" .)