Denial from Number Ten, initially (3)
I believe the answer is:
not
'denial' is the definition.
'number ten initially' is the wordplay.
'number' becomes 'no' (abbreviation).
'initially' indicates taking the first letters.
The first letter of 'ten' is 't'.
'no'+'t'='NOT'
'from' acts as a link.
(Other definitions for not that I've seen before include "Having close-cut hair" , "logically, operation needed" , "Negatory word" , "In no way, never" , "Ton (anag.)" .)