Tore away from Waterloo and went missing (4)
I believe the answer is:
awol
'missing' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for awol that I've seen before include "unaccounted for" , "Of soldier, illegally absent - initially" , "Take unofficial leave (abbrev.)" , "Missing without permission" , "Absent without leave (abbr.)" .)