As I see this, the wordplay gives RIPOST as the answer.
AfteR last letter = R + I POST (I send).
In the dictionary on this site the following definition is given.
Ripost In fencing, a return thrust after a parry.
I agree with you that "snappy answer" should be riposte.
I suspect PIGOUT is an error. I've never particularly looked before, but I can't recall ever seeing a correction or apology printed for a crossword error. But let's wait and see next week's paper.