Contradiction (8)
'contradiction' is the definition.
(I know that paradox is a type of contradiction)
This is all the clue.
(Other definitions for paradox that I've seen before include "Statement which seems contradictory but is true" , "there's a contradiction here!" , "Seemingly sound, though self-contradictory, statement" , "Seemingly absurd statement that may be true" , "Apparently contradictory statement" .)
'contradiction' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for denial that I've seen before include "Nailed (anag.)" , "Rejection of a request" , "Declaration that something is untrue" , "Refusal to believe an unacceptable truth" , "Refusal to accept an unpalatable truth" .)
(Other definitions for oxymoron that I've seen before include "It sends mixed messages" , "Figure of speech joining contradictory terms" , "'Figure of speech, it contains contradictory terms (8)'" , "Figure of speech using contradictory terms" , "Phrase or sentence with inherent contradiction" .)