Sure one or other is wrong (9)
I believe the answer is:
erroneous
'is wrong' is the definition.
(similar in meaning)
'sure one or other' is the wordplay.
'other' indicates an anagram.
'sure'+'one'+'or'='sureoneor'
'sureoneor' is an anagram of 'ERRONEOUS'.
(Other definitions for erroneous that I've seen before include "with mistakes" , "Incorrect, wrong" , "not right" , "Mistaken - inaccurate" , "Mistaken, in error" .)