When redEYEs fly (9)
I believe the answer is:
overnight
'when redeyes fly' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for overnight that I've seen before include "Until morning; suddenly" , "Lasting from dusk to dawn" , "Very quickly" , "from one day to the next" , "Extending from dusk to dawn" .)