Leaving do ahead of spring
I believe the answer is:
farewell
'leaving' is the definition.
(farewell is a kind of leaving)
'do ahead of spring' is the wordplay.
'do' becomes 'fare' ('fare' can be a synonym of 'do').
'ahead of' is a charade indicator (letters next to each other) (I've seen this in other clues).
'spring' becomes 'well' (I've seen this before).
'fare'+'well'='FAREWELL'
(Other definitions for farewell that I've seen before include "All the best" , "Say goodbye" , "Wish on leave-taking" , "symphony" , "Departure" .)