Lickety-split (4)
I believe the answer is:
asap
'lickety-split' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for asap that I've seen before include "Notation for as quickly as you can" , "Common acronym for quick-as-you-can" , "'At the earliest moment, initially (4)'" , "As soon as possible (abbrev.)" , "Initials notation meaning with all possible speed" .)