This writer lacked a single bit of inspiration? You surprise me! (1,3,2,4)

'you surprise me' is the definition.
(both are expressions of disbelief)

'this writer lacked a single bit of inspiration?' is the wordplay.
I cannot really see how this works, but
'writer' could be 'i' (the person who is writing these clues) and 'i' is found within the answer.
'lacked' could be 'hadno' (I've seen this in another clue) and 'hadno' is found within the answer.
'a' is found in the answer.
'single' could be 'i' (one) and 'i' is found within the answer.
This may be the basis of the clue (or it may be nonsense).