In two ways a big success (3)
I believe the answer is:
wow
'success' is the definition.
(I have seen 'Huge success' mean 'wow' so perhaps 'success' could also mean 'wow')
'in two ways a big' is the wordplay.
'in' indicates the answer is hidden within the clue.
'WOW' is hidden in the letters of 'two ways big'.
(Other definitions for wow that I've seen before include "Expression of great admiration" , "that's incredible!" , "Exclamation of admiration - another palindrome" , "Impress hugely" , "Cor! - huge success" .)