Refusal (6)
I believe the answer is:
denial
'refusal' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for denial that I've seen before include "Act of asserting that something alleged is not true" , "Refusal, abnegation" , "Negation" , "Refusal to accept an unpalatable truth" , "Saying it isn't so" .)