Without delay, initially (4)
I believe the answer is:
asap
'without delay' is the definition.
(as soon as possible)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for asap that I've seen before include "As soon as you can, initially" , "Notation for as quickly as you can" , "Common acronym for quick-as-you-can" , "Notation meaning with minimum delay" , "yesterday?" .)