Drop into abyss, a goner (3)
I believe the answer is:
sag
'drop' is the definition.
(sagging is a kind of dropping)
'into abyss a goner' is the wordplay.
'into' indicates a hidden word.
'SAG' can be found hidden inside 'abyss a goner'.
(Other definitions for sag that I've seen before include "Drop" , "Droop in the middle - it's gas" , "Cave in" , "Spinach as used in Indian cookery" , "Decline" .)