Daniel, in play, saying it isn't so (6)
I believe the answer is:
denial
'saying it isn't so' is the definition.
(I've seen this before)
'daniel in play' is the wordplay.
'in play' indicates an anagram (letters play around).
'daniel' with letters rearranged gives 'DENIAL'.
(Other definitions for denial that I've seen before include "Refusal to accept an unpalatable truth" , "Repudiation" , "Renunciation" , "Rejection of a request" , "Rejection or refusal" .)