Examination in science ultimately failing a student (8)
I believe the answer is:
physical
'examination in science' is the definition.
'physical' can be an answer for 'science' (physical science is a kind of science). I am not certain of the 'examination in' bit.
'ultimately failing a student' is the wordplay.
'ultimately failing' becomes 'physic' (I can't explain this - if you can you should believe this answer much more).
'student' becomes 'L' (as in L-plates for learner drivers).
'physic'+'a'+'l'='PHYSICAL'
Can you help me to learn more?
(Other definitions for physical that I've seen before include "Relating to the body, not the mind" , "Medical fitness examination" , "Check-up" , "Involving bodily contact" , "Medical check" .)