Affirmed wrong date given about international match (8)
I believe the answer is:
attested
'affirmed' is the definition.
(attesting is a kind of affirming)
'wrong date given about international match' is the wordplay.
'wrong' indicates anagramming the letters.
'given about' means one lot of letters goes inside another.
'international match' becomes 'test' (I've seen this before).
'date' is an anagram of 'ated'.
'ated' enclosing 'test' is 'ATTESTED'.
(Other definitions for attested that I've seen before include "Declared that something was true" , "Witnessed formally" , "Certified, vouched" , "Affirmed to be true" , "Declared to be true or genuine" .)