A puzzle full of holes? (6)
I believe the answer is:
riddle
'a puzzle' is the definition.
(a riddle is a puzzle or problem)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for riddle that I've seen before include "Brain-teaser and coarse sieve" , "The large sieve is a puzzle" , "Kind of puzzle or coarse sieve" , "Sphinx's conundrum?" , "Puzzle or strainer" .)