Inordinately easy start to Toughie? Till now! (2,3)
I believe the answer is:
as yet
'till now' is the definition.
(I've seen this in another clue)
'inordinately easy start to toughie?' is the wordplay.
'inordinately' indicates anagramming the letters.
'start to' says to take the initial letters.
The first letter of 'toughie' is 't'.
'easy' anagrammed gives 'asye'.
'asye'+'t'='AS YET'
(Other definitions for as yet that I've seen before include "Thus far" , "Up to this point in time" , "Up till now" .)