Two bad grades in certain exams and tests (7)
I believe the answer is:
ordeals
'tests' is the definition.
(I have seen 'difficult tests' mean 'ordeals' so perhaps 'tests' could also mean 'ordeals')
'two bad grades in certain exams' is the wordplay.
'two bad grades' becomes 'de' (I am not sure about this - if you are sure you should believe this answer much more).
'in' indicates putting letters inside.
'certain exams' becomes 'orals' (I've seen this in another clue).
'de' put inside 'orals' is 'ORDEALS'.
'and' is the link.
Can you help me to learn more?
(Other definitions for ordeals that I've seen before include "Tribulations" , "Testing experiences" , "Difficult experiences, hard times" , "difficult tests" , "Trying experiences" .)