Sleepy, I'd changed quickly (8)
I believe the answer is:
speedily
'quickly' is the definition.
(I know that quickly can be written as speedily)
'sleepy i'd changed' is the wordplay.
'changed' is an anagram indicator.
'sleepy'+'id'='sleepyid'
'sleepyid' with letters rearranged gives 'SPEEDILY'.
(Other definitions for speedily that I've seen before include "Quickly, rapidly" , "In haste" .)