Gone but not forgotten (4)
I believe the answer is:
awol
'gone but not forgotten' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for awol that I've seen before include "Truant (or just missing)" , "Absent without leave (abbr.)" , "unaccounted for" , "Missing without permission" , "Of soldier, illegally absent - initially" .)