Beginning of Lent (3,9)
'beginning of lent' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ash wednesday that I've seen before include "Beginning of Lent" , "Time to start doing without" , "Date in church calendar" , "Poem by T.S. Eliot" , "First day of Lent" .)
(Another definition for ashwednesday that I've seen is " fast start".)