Hateful duo is nothing special (6)
I believe the answer is:
odious
'hateful' is the definition.
(similar in meaning)
'duo is nothing special' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'special' is an anagram indicator.
'duo'+'is'+'o'='duoiso'
'duoiso' anagrammed gives 'ODIOUS'.
(Other definitions for odious that I've seen before include "Detestable, greatly disliked" , "Really obnoxious, generally disliked" , "Loathsome and repulsive" , "Extremely unpleasant" , "Contemptible" .)