Owing (3)
'owing' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for due that I've seen before include "Owed - expected" , "Proper; owed" , "deserts" , "Required; proper" , "Outstanding" .)
'owing' is the definition.
This is the entire clue.
(Another definition for in debt that I've seen is " Owing money".)
(Other definitions for indebt that I've seen before include "Owing something" , "Owing, perhaps money" .)