Acerbic representation of Maori cousin (11)
I believe the answer is:
acrimonious
'acerbic' is the definition.
(thesaurus)
'representation of maori cousin' is the wordplay.
'representation of' indicates an anagram (I've seen this in other clues).
'maori'+'cousin'='maoricousin'
'maoricousin' with letters rearranged gives 'ACRIMONIOUS'.
(Other definitions for acrimonious that I've seen before include "Angry, bitter" , "Hostile" , "Producing bad feelings" .)