Puzzle that's full of holes? (6)
I believe the answer is:
riddle
'puzzle' is the definition.
(a riddle is a puzzle or problem)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for riddle that I've seen before include "mystery" , "unsolved problem" , "It may have an answer" , "Run through" , "Difficult problem or coarse sieve" .)