You're welcome? Never! (3,2,3)
I believe the answer is:
not at all
I believe this clue is a double definition.
'you're welcome?' is the first definition.
(I've seen this before)
'never' is the second definition.
(Other definitions for not at all that I've seen before include "forget it" , "acceptance of apology" , "By no means - polite disclaimer" , "You're welcome" , "denial" .)