Satirical author's left with riddle (4)
I believe the answer is:
sift
'riddle' is the definition.
(riddle can mean to sieve or sift)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for sift that I've seen before include "Remove lumps from, eg, flour" , "Examine minutely" , "Sieve, examine closely" , "screen" , "Separate out - examine closely" .)