Badly missing (4)
I believe the answer is:
awol
'missing' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for awol that I've seen before include "Army offence of being missing from duty, briefly" , "'Absent without permission, initially (4)'" , "Absent without leave (abbrev.)" , "Absent without permission, in short" , "Not present when supposed to be" .)