Crack setter often leaves vague enigmas initially (5)
I believe the answer is:
solve
'crack' is the definition.
(thesaurus)
'setter often leaves vague enigmas initially' is the wordplay.
'initially' says to take the initial letters.
The first letters of 'setter often leaves vague enigmas' is 'SOLVE'.
(Other definitions for solve that I've seen before include "Unravel (a problem)" , "Find the answer to a mystery" , "Get the answers" , "Find an answer to (a problem)" , "Complete crossword" .)