Free, led to crack puzzle (6)
I believe the answer is:
riddle
'puzzle' is the definition.
(riddling is a kind of puzzling)
'free led to crack' is the wordplay.
'free' becomes 'rid' ('rid' can be a synonym of 'free'**).
'to crack' is an anagram indicator (I've seen 'cracked' mean this).
'led' anagrammed gives 'dle'.
'rid'+'dle'='RIDDLE'
(Other definitions for riddle that I've seen before include "Kind of puzzle or coarse sieve" , "It may have an answer" , "Ingenious puzzle - sieve" , "Cryptic verse" , "Question to test ingenuity, something puzzling" .)