Contradiction in terms (7)
I believe the answer is:
paradox
'contradiction in terms' is the definition.
(paradox is a kind of contradiction in terms)
This is the entire clue.
(Other definitions for paradox that I've seen before include "Seeming contradiction" , "Seemingly sound, though self-contradictory, statement" , "Absurd or self-contradictory statement" , "Seemingly absurd statement that may be true" , "Statement that seems contradictory but expresses truth" .)