Not passing because of a defect (7)
I believe the answer is:
failing
'not passing' is the definition.
('fail' is the opposite to 'pass')
'because of a defect' is the wordplay.
I cannot quite see how this works, but
'a' is within the answer.
The remaining letters 'filing' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for failing that I've seen before include "Character weakness" , "Weak point" , "Flunking" , "Defect" , "conking out" .)