Riddle (6)
'riddle' is the definition.
(synonyms)
This is all the clue.
(Other definitions for enigma that I've seen before include "Difficult problem" , "Solution to mystery" , "Mystery U puzzle" , "Conundrum" , "Mysterious person" .)
'riddle' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for conundrum that I've seen before include "Difficult problem" , "Puzzle, riddle" , "Puzzling problem" , "That's puzzling" , "anagram" .)
'riddle' is the definition.
(riddle can mean to sieve or sift)
This is the entire clue.
(Other definitions for sift that I've seen before include "Riddle, sieve" , "Pass though a sieve" , "Distinguish as with a riddle" , "Remove lumps from, eg, flour" , "Put through a sieve" .)
'riddle' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sieve that I've seen before include "Utensil for straining or sifting food" , "Jumblies' vessel" , "Device for separating lumps" , "Fine riddle" , "Colander" .)
'riddle' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for mystery that I've seen before include "Type of play" , "Something difficult to understand" , "Something strange and inexplicable" , "Unexplained phenomenon" , "thriller" .)