Box where there's a lack of evidence, almost up-ended (6)
I believe the answer is:
carton
'box' is the definition.
(carton is a kind of box)
'there's a lack of evidence almost up-ended' is the wordplay.
'there's a lack of' becomes 'no' (lack of money is no money).
'evidence almost' becomes 'trac' (I can't justify this - if you can you should believe this answer much more).
'up-ended' says the letters should be written backwards (in a down clue, letters go up).
'no'+'trac'='notrac'
'notrac' written backwards gives 'CARTON'.
'where' is the link.
Can you help me to learn more?
(Other definitions for carton that I've seen before include "fictional lawyer" , "A cardboard container as for milk" , "Box made of cardboard" , "Cardboard or plastic container" , "He did a far, far better thing" .)