Number, note, new (3)
I believe the answer is:
ten
'number' is the definition.
(I know that ten is a type of large integer)
'note new' is the wordplay.
'note' becomes 'te' (musical note).
'new' becomes 'n' (abbreviation as in New Testament NT).
'te'+'n'='TEN'
(Other definitions for ten that I've seen before include "Cardinal number" , "Base of decimal system" , "PM's address, Downing St" , "X-WORD" , "Five times two" .)